MOHAMEDAMINE Ghebouli

سعدي زهية

Contribution à l'étude des propriétes physique de la famille pérovskites en utilisant la théorie du pseudo-potentiel

Radja Nour El houda , Ben Salem Souhyla

Caractirisation structurale, électronique et optique des semi-conducteurs CdTe et CdS pour des applications dans les cellules photovoltaiques

Larbi Radhia

Etude des propriétes structurales, électroniques et optiques des semiconducteurs CdS et ZnO pour des application photovoltaiques

Zeghad Aldjia

Etude des propriétes structurales, électroniques et optiques des semiconducteurs GaX (X P, As et Sb) par la méthode Ab-initio

بن هدوقة ايمان

Etude structural et electronique des semi-conducteurs ZnS et ZnO pour des applications photovoltaique

علالي بلال

Etude structural , electronique et élastiques des composées BaIrO3 et BaBbO3 par Ab-initio

بن زروق نبيل

Etude par simulation desv propriétes structurales et électroniques des semi-conducteurs

لعويجي حورية

Etude des propriétés structurales, élastique et électroniques du semi-conducteur AlP par la méthode ab-initiotio

بن ساعد شريف

Etude des propriétés structurales, élastique et électroniques des semi-conducteurs par la méthode Ab-Initio

This investigation undertakes a comprehensive exploration into the inherent structural, elastic, and mechanical attributes exhibited by ZnX compounds, with a specific focus on instances where X corresponds to O, Te, and S. Employing the robust framework of density functional theory (DFT) in conjunction with the CASTEP software, this study employs the Local Density Approximation (GGA) to meticulously scrutinize the cross-correlation function. The computational outcomes encompass a thorough analysis of lattice modulus and mechanical elasticity traits, which are meticulously validated against empirical observations and theoretical predictions. These findings collectively underscore the tantalizing potential of ZnX compounds (where X embodies O, Te, and S) within the realm of optoelectronic applications, notably encompassing solar cell technologies, as a result of their intrinsically favorable attributes. Furthermore, the integration of intricate insights concerning elastic and mechanical properties offers an enriched comprehension of the applicability of these compounds, particularly in the context of flexible solar cell advancements. The prowess of the CASTEP program as an indispensable tool for attribute estimation is notably evident through the application of GGA-based cross-correlation function calculations. The amalgamation of theoretical insights and computational advancements achieved in this study contributes substantively to the expanding domain of materials science. In conclusion, this work serves as a pivotal stepping stone towards refining material design strategies for cutting-edge optoelectronic devices, thereby paving the way for innovation and advancement in this technologically pivotal field. Keywords: ZnX compounds; Structural properties; Elastic properties; Mechanical properties; Density functional theory (DFT); CASTEP software; Local Density Approximation (GGA); Lattice modulus;

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Idris BOUCHAMA , MohamedAmine GHEBOULI , Chihi tayeb, ,(2023-12-13), Enhancing ZnX (X = O, Te, S) Compound Properties via LDA Approach and CASTP Program: Computational Investigation of Structural, Elastic, and Mechanical Aspects,Enhancing ZnX (X = O, Te, S) Compound Properties via LDA Approach and CASTP Program: Computational Investigation of Structural, Elastic, and Mechanical Aspects,Laghouat, Algeria

By first-principles calculations with density functional theory and a pseudopotential approach, the structural, electronic, and optical properties of the anhydrous 4C16H10Br2O2 Bis (2-Bromobenzoyl) Methane crystals in Pbnc (N◦60) and P21/c (N◦14) space group are investigated. All computations are determined by a generalized gradient approximation, local density approximation and an ultra-soft pseudopotential. The calculated equilibrium parameters are in good agreement with their available experimental data. This calculation shows that the GGA/PW91 functional overestimate the lattice constant, unlike the LDA/CA-PZ. The Br–C bond distance of 1.856 (1.902) Å is comparable with experimental value of 1.901 (1.896) Å in Pbnc (P21/c) space groups. The direct band gap nature is obtained for both space groups Pbnc and P21/c, since the maximum of the valence band and the minimum of the conduction band are both situated at the YA center.

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MohamedAmine GHEBOULI , , (2023-12-05), Prediction study of structural, electronic and optical properties of 4C16H10Br2O2 Bis (m-bromobenzoyl) methane crystals, Biochemistry and Biophysics Reports, Vol:37, Issue:37, pages:101601, sciencediret

By first-principles calculations with density functional theory and a pseudopotential approach, the structural, electronic, and optical properties of the anhydrous 4C16H10Br2O2 Bis (2-Bromobenzoyl) Methane crystals in Pbnc (N°60) and P21/c (N°14) space group are investigated. All computations are determined by a generalized gradient approximation, local density approximation and an ultra-soft pseudopotential. The calculated equilibrium parameters are in good agreement with their available experimental data. This calculation shows that the GGA/PW91 functional overestimate the lattice constant, unlike the LDA/CA-PZ. The Br–C bond distance of 1.856 (1.902) Å is comparable with experimental value of 1.901 (1.896) Å in Pbnc (P21/c) space groups. The direct band gap nature is obtained for both space groups Pbnc and P21/c, since the maximum of the valence band and the minimum of the conduction band are both situated at the YA center.

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MohamedAmine GHEBOULI , karim BOUFERRACHE , R. Boudissa, Z. Zerrougui, , (2023-12-05), Prediction study of structural, electronic and optical properties of 4C 16 H 10 Br 2 O 2 Bis (m-bromobenzoyl) methane crystals, Biochemistry and Biophysics Reports, Vol:37, Issue:, pages:101601, Elsevier

Ab-initio simulations based on density functional theory as contained in the WIEN2k code using GGA, GGA+U, and mBJ approximations were used to perform the calculations. The energy of cohesion is minimal for FeMnCrSb, indicating that it is the most stable structure, with a lattice constant of 5.95 Å and 6.2184 Å for GGA and GGA+U. The ferromagnetic state is less stable than ferrimagnetic states in all studied quaternary Heusler. All the band structures are metallic, with the exception of the spin up case using GGA+U and mBJ approaches, where the semiconducting character is predicted. The amount of absorption and band gap validates the candidature of CoFeCrAl, CoFeMnSi, CoMnCrSi, and FeMnCrSb as absorber materials for photovoltaic devices. The high values of 0.8, 0.9, 0.95 and 1 for figure of merit (ZT) at 300 K were obtained for CoFeMnSi, CoFeCrAl, CoMnCrSi, and FeMnCrSb allowing their use in spintronic and thermoelectric applications. The resistivity of studied quaternary alloys is little sensitive to the temperature, while the electronic conductivity and power factor are proportional to the temperature

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MohamedAmine GHEBOULI , ,(2023-12-02), the structural properties, optoelectronic and magnetic behaviour of CoFeMtAs quaternary heusler alloy,First national conférence on physics and its application,Bousaada

The goal of this study is based on the determination of the half-metallic ferromagnetic features of V-doped Cu2O alloys (Cu2(1-x)V2xO (x = 0, 0.25, 0.50, 0.75 and 1)) using both GGA + U and TB-mBJ-GGA approximations (GGA: the generalized gradient approximation) within the accurate full potential linearized augmented plane wave plus local orbitals (FP-LAPW + lo) method implemented in the WIEN2k package. The structural properties are computed by using the GGA approximation in order to find the equilibrium structural parameters of each alloy, such as: lattice parameter, bulk modulus and its first-pressure derivative. The electronic properties calculated by TB-mBJ-GGA and GGA + U approximations show the complete half-metallicity of Cu1.50V0.50O, CuVO, Cu0.50V1.50O and V2O alloys, in fact, all the half-metallic gaps (EHM) of the compete half-metals are given in this study. The magnetic properties of the studied alloys show that the majority of the total magnetic moment (MTot) comes from the V atom with small contributions from Cu atom and the interstitial zone. The N0α and N0β exchange-splitting constants are given in order to analyze the contributions to conduction and valence bands during the exchange and splitting process. Furthermore, the hybridization between the 2p-O and 3d-V states (p- d hybridization) is the cause for the appearance of feeble magnetic moments on the non-magnetic Cu and O sites and the reduction of the atomic magnetic moment of the V atom.

Citation

MohamedAmine GHEBOULI , , (2023-11-30), Half-metallic ferromagnetic features of V-doped Cu2O alloys: TB-mBJ and DFT + U insights, Results in Physics, Vol:57, Issue:57, pages:107368, Elsevier

In the pursuit of sustainable porcelain production, this research examines the potential of using recovered automotive glass as a substitute for traditional feldspar, specifically feldspar imported from Spain. Porcelain samples were sintered at different temperatures and with varied proportions of automotive glass. The crystalline phases formed post-sintering were determined through X-ray diffraction and quantified by dissolving the porcelain in concentrated hydrofluoric acid. Results revealed that the inclusion of automotive glass, owing to its dissolved oxide content, accelerated the porcelain melting process and led to an increase in the vitreous phase. Notably, anorthite phases became dominant and mullite formation was evident at 1100 ◦C, stabilizing in samples G00 and G10, and then increasing at 1200 ◦C due to the emergence of secondary mullite. This secondary mullite forms from the residual silica after the primary mullite formation and the aluminium in the feldspars, which is about 17 %. For samples G20 and G30, only primary mullite was observed due to the decreased aluminium content resultant from feldspar replacement by glass. These findings underscore the viability of automotive glass in porcelain production, providing a sustainable and effective alternative to feldspar

Citation

MohamedAmine GHEBOULI , , (2023-11-23), Effect of temperature and glass content on crystalline phases in porcelain sintered with recovered automotive glass, Heliyon, Vol:9, Issue:9, pages:e22554, Elseier

The crystal structure, mechanical, electronic, optical and thermoelectric characteristics of Cs2MCl6 (M = Se, Sn, Te and Ti) cubic double perovskites are studied within GGA, GGA-mBJ and EV-GGA functionals. The M − Cl bond lengths are shorter and especially in Cs2TiCl6 double perovskite, which reflects the strong interaction between M and Cl atoms and this is correlated with its better chemical stability. The negativity of formation energy and Helmholtz free energy and no imaginary phonon modes throughout the Brillouin zone confirm the thermal, thermodynamic and dynamical stability of these double perovskites. Semiconductors Cs2MCl6 (M = Se, Sn, Te and Ti) double perovskites with flat conduction and valence bands, and an indirect band gap are p-type carriers. A high Seebeck coefficient, adequate ZT values and non-toxicity make these compounds attractive for thermoelectric applications at high temperature and spintronic technology. The empty first conduction band corresponds to their band gap, and the transition occurs from Cl-p to (Se-p, Sn-p, Te-p and Ti-d). The high static dielectric constant and the intense peak of the real part in the ultraviolet energy range favor less the recombination rate of charge carriers and their use in optoelectronic devices. The indirect band gap, high absorption in ultraviolet energy, high static refractive index make these cubic double perovskites as ideal materials for solar cell application

Citation

MohamedAmine GHEBOULI , , (2023-11-23), Crystal structure, mechanical, electronic, optical and thermoelectric characteristics of Cs2MCl6 (M = Se, Sn, Te and Ti) cubic double perovskite, Results in Physics, Vol:56, Issue:56, pages:107183, elsevier

The Quaternary Heusler alloys CoFeXAs (X = Cr, Mn and V) fully spin-polarized with half-metallic stability, show low direct band gap, high absorption in the ultraviolet light, high spin polarization and adequate Seebeck coefficient. CoFeCrAs, CoFeMnAs and CoFeVAs have an integer magnetic moment of 4 μB, 5 μB and 3 μB according to the Slater-Pauling rule. The obtained minimal energy favors the type I CoFeVAs alloy over the type III CoFeCrAs and CoFeMnAs alloys. For CoFeCrAs and CoFeMnAs alloys, there is no band gap close to the Fermi level in the minority-spin, suggesting that they are direct Г–Г band gap semiconductors. Three-dimensional Co, Fe, and Mn atoms hybridized strongly, with little input from V and As atoms. Co, Fe, Cr, and Mn all have parallel magnetic moments, which results in ferromagnetic interactions between these atoms and gives these elements their ferromagnetic character.

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MohamedAmine GHEBOULI , , (2023-10-24), Structural stability, opto-electronic, magnetic and thermoelectric properties of half-metallic ferromagnets quaternary Heusler alloys CoFeXAs (X = Mn, Cr and V), Solid State Communications, Vol:377, Issue:377, pages:115366, elsevier

The main objective of this research is the explanation of the replacement of feldspar limestone imported from Spain with recycled automotive glass, in order to reduce waste and promote environmental sustainability. Details and efforts of making porcelain ceramics from local raw materials such as quartz, kaolin and glass are also given. Replacing the feldspar with reclaimed automotive glass shows the effect of the Na2O and CaO solvents contained in the glass on the sintering and crystallization of the studied porcelain. The results showed that the added glass contributes to the reduction of the density and the acceleration of the sintering process, by occupying the sites of the open spaces, observed in the samples not containing feldspars. By reaching a nonporous ratio at a temperature of 1000∘C, the melting of the material is accelerated due to the dissolved oxides it contains, in addition to the linear shrinkage rate in samples that contain a lot of glass reaching the normal level of porcelain (about 12%) at low temperature compared to ordinary porcelain.

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MohamedAmine GHEBOULI , , (2023-10-13), Sustainable porcelain ceramics production using local raw materials and recycled automotive glass, Modern Physics Letters B, Vol:5, Issue:5, pages:2450064, World Scientific Publishing Company

Zinc monochalcogenides, specifically ZnS serve as exemplary representatives of II-VI semiconductors and have the ability to adopt either zinc-blende (ZnX-z) or wurtzite (ZnX-w) crystal structures. Notably, ZnX-z phases exhibit optical isotropy, while ZnX-w phases display anisotropy, with the c-axis serving as the polar axis. ZnS featuring a wide direct band gap of approximately 3.37 eV at room temperature, emerges as a quintessential semiconductor employed extensively in optoelectronic applications. Furthermore, ZnS exhibits transparency within the visible light spectrum and possesses the added advantage of environmental friendliness, attributed to the abundant presence of zinc in the Earth's crust. Among the family of IIB-VIA compounds, namely ZnS, this material crystallizes in the cubic zinc-blende structure under ambient pressure, boasting direct energy band gaps. Notably, these wide band-gap semiconductors are of paramount interest due to their capability to emit light even at room temperature. Utilizing computational tools such as CASTEP offers a robust means for designing and enhancing these materials, facilitating the development of advanced optoelectronic devices. In this study, we delved into the electronic structure and optical characteristics of ZnS systems, employing first principles through the ultra-smooth pseudopotential approach of density functional theory and the generalized gradient approximation method implemented with CASTEP. Our investigation yielded the following findings: The network parameters exhibited varying values, making it feasible to deposit these materials on different substrates. The binary alloy holds particular interest due to its wide bandgap 2.698 eV for ZnS. The results obtained for the structural, physical, and optical properties closely align with existing theoretical and experimental data, affirming the accuracy of our calculation methodology. The properties of pure ZnS materials suggest significant potential for use in solar cells.

Citation

MohamedAmine GHEBOULI , ,(2023-10-10), Comprehensive investigation of ZnS: Structural properties, Elastic constants and their crucial role in environmental protection and clean energy production,,The second International conference of nanotechnology for environmental protection and clean energy production ICNEP-2023,Freres Mentouri University - Constantine I,Mentouri University - Constantine I

The structural, electronic, optical and thermodynamic properties of SrxCa1-xO, BaxSr1-xO and BaxCa1-xO ternary alloys in NaCl phase were studied using pseudo-potential plane-wave method within the density functional theory. We modeled the alloys at some selected compositions with ordered structures described in terms of periodically repeated supercells. The dependence of the lattice parameters, band gaps, dielectric constants, refractive indices, Debye temperatures, mixing entropies and heat capacities on the composition x were analyzed for x = 0, 0.25, 0.50, 0.75 and 1. The lattice constant for SrxCa1-xO and BaxSr1-xO exhibits a marginal deviation from the Vegard’s law, while the BaxCa1-xO lattice constant exhibits an appreciable upward bowing. A strong deviation of the bulk modulus from linear concentration dependence was observed for the three alloys. The microscopic origins of the gap bowing were detailed and explained. The composition dependence of the dielectric constant and refractive index was studied using different models. The thermodynamic stability of these alloys was investigated by calculating the phase diagram. The thermal effect on some macroscopic properties was investigated using the quasi-harmonic Debye model. There is a good agreement between our results and the available experimental data for the binary compounds which may be a support for the results of the ternary alloys reported here for the first time.

Citation

MohamedAmine GHEBOULI , ,(2023-10-09), Structural, electronic, optical and thermodynamic properties of SrxCa1-xO, BaxSr1-xO and BaxCa1-xO alloys,Second international conférence of nanotechnology for environmental protection ans clean energy protection,University mentouri constantine 1

Structural, elastic, mechanical and electronic properties of pure and zinc-doped SrTiO3 at the concentration in the range (1–10%) are studied by first-principles calculations. The structural parameters of synthesized compounds agree well with the standard data depicting the growth of stable compounds. A slight obvious increase in the lattice constant of 3.9245Å is observed in Zn-doped SrTiO3 due to the deviation of the atomic radii of Zn and Ti. Elastic constants and mechanical parameters of SrTiO3 are closer to their available theoretical and experimental data. The investigated compounds exhibit brittle behavior for all Zn ratios. The doping zinc concentration reduces the indirect band gap value. The doping concentration 2%, gives a band gap value closer to the experimental one. The band gap of pure SrTiO3 is 1.827eV and after doping with Zn for concentration from 1% to 10%, the optimized values are 1.970, 1.886, 1.802, 1.718, 1.635, 1.552, 1.470, 1.389, 1.310, 1.231 and 1.154eV.

Citation

MohamedAmine GHEBOULI , , (2023-08-14), Structural, elastic, mechanical and optoelectronic properties of zinc-doped SrTiO3 perovskite compounds, Modern Physics Letters B, Vol:38, Issue:1, pages:2350200, world scientific

The purpose of this research is to investigate the structural, electronic, and optical properties of ZnX compounds, particularly those with X = Te, S, and O, which have direct bandgaps that make them optically active. To gain a better understanding of these compounds and their related properties, we conducted detailed calculations using density functional theory (DFT) and the CASTEP program, which uses the generalized gradient approximation (GGA) to estimate the cross-correlation function. Our results for lattice modulus, energy bandgap, and optical parameters are consistent with both experimental data and theoretical predictions. The energy bandgap for all compounds is relatively large due to an increase in s-states in the valence band. Our findings suggest that the optical transition between (O - S - Te) - p states in the highest valence band and (Zn - S - O) - s states in the lowest conduction band is shifted to the lower energy band. Therefore, ZnX compounds (X = Te, S and O) are a promising option for optoelectronic device applications, such as solar cell materials

Citation

MohamedAmine GHEBOULI , , (2023-06-07), AB-INITIO STUDY OF STRUCTURAL, ELECTRONIC AND OPTICAL PROPERTIES OF ZnX (X = Te, S and O): APPLICATION TO PHOTOVOLTAIC SOLAR CELLS, EAST EUROPEAN JOURNAL OF PHYSICS., Vol:3, Issue:3, pages:413-433, Springer

All studied properties of FeX (X = Pt, Pd) in austenitic and martensitic phases are investigated within Local Spin Density Approximation as exchange functional. The structural parameters at equilibrium for ferromagnetic tetragonal FePt and FePd a = 3.911 Å, c = 3.842 Å and a = 3.816 Å, c = 3.736 Å, and the lattice constant for ferromagnetic cubic FePt and FePd a = 4.9304 Å and a = 4.905 Å agree well with their available theoretical and experimental data. FePd and FePt formation enthalpy of the martensitic phase was 12625.73 eV and 39414.97 eV, while in the austenitic phase it was 12625.33 eV and 39413.97 eV. The rock-salt FePd (tetragonal FePt) is more stable than tetragonal FePd (rock-salt FePt). For both compounds, the anisotropy is more pronounced in the martensitic phase

Citation

MohamedAmine GHEBOULI , , (2023-05-15), Study of structural, elastic, mechanical, electronic and magnetic properties of FeX (X=Pt, Pd) austenitic and martensitic phases, Solid State Sciences, Vol:141, Issue:107211, pages:107211, lsevier

Cet ouvrage qui comprend des exercices corrigés a été réalisé dans le but de faciliter la compréhension de la structure de la matière et les liaisons chimiques. Ce document est destiné principalement aux étudiants de la première année des filières Sciences de la Matière (SM), Sciences Techniques (ST), et Sciences de la Nature et de la Vie (SVI). Cette édition d'exercices corrigés permet aux étudiants de ces filières d’acquérir une méthodologie adéquate pour résoudre les problèmes de la chimie de l’atome. Ce manuscrit se compose de cinq parties, où on étudie principalement la structure de l'atome, les modèles quantique et ondulatoire de l'atome de Bohr, la classification périodique et la structure électronique des éléments ainsi que leurs propriétés et enfin les liaisons chimiques entre atomes et molécules. Chaque chapitre comprend une série d’exercices choisie pour son intérêt et sa diversité. On reporte aussi le corrigé détaillé de cette série afin que les étudiants puissent assimiler le cours de cette matière. On propose dans le premier chapitre des exercices de connaissances générales sur la structure de l’atome, sur les isotopes et les défauts de masse. Le second chapitre est consacré au calcul des différents paramètres de l’atome d’hydrogène et des ions hydrogénites selon le modèle de Bohr. L'étude des différentes séries spectrales de l’atome d’hydrogène est également bien détaillée. Dans le troisième chapitre, on traite le modèle ondulatoire de l’atome qui comprend la relation de Louis De Broglie, l'équation de Schrödinger, les fonctions d’ondes et les orbitales atomiques. On détermine aussi les structures électroniques des éléments en utilisant les règles de remplissage des électrons dans les différentes couches et sous-couches de l’atome. Les exercices que contient le chapitre quatre servent à déterminer la structure électronique d’un atome et son numéro atomique suivant son classement dans le tableau périodique. Ces exercices permettent aussi de trouver le groupe ou la période auxquels appartient l’atome. Le dernier chapitre traite des exercices d'application sur les différentes liaisons chimiques possibles entre les atomes et molécules. Mon souhait est que ce modeste travail améliore l'encadrement et la formation dans notre Université et qu'il sera d'une grande importance à nos étudiants pour acquérir une base solide en chimie de la matière.

Citation

MohamedAmineGHEBOULI , ,(2023-05-09); structure de la matière exercices corriges,Mohamed Boudiaf Msila,

Ab-initio simulations based on density functional theory as contained in the WIEN2k code using GGA, GGA+U, and mBJ approximations were used to perform the calculations. The energy of cohesion is minimal for FeMnCrSb, indicating that it is the most stable structure, with a lattice constant of 5.95 Å and 6.2184 Å for GGA and GGA+U. The ferromagnetic state is less stable than ferrimagnetic states in all studied quaternary Heusler. All the band structures are metallic, with the exception of the spin up case using GGA+U and mBJ approaches, where the semiconducting character is predicted. The amount of absorption and band gap validates the candidature of CoFeCrAl, CoFeMnSi, CoMnCrSi, and FeMnCrSb as absorber materials for photovoltaic devices. The high values of 0.8, 0.9, 0.95 and 1 for figure of merit (ZT) at 300 K were obtained for CoFeMnSi, CoFeCrAl, CoMnCrSi, and FeMnCrSb allowing their use in spintronic and thermoelectric applications. The resistivity of studied quaternary alloys is little sensitive to the temperature, while the electronic conductivity and power factor are proportional to the temperature.

Citation

MohamedAmine GHEBOULI , , (2023-01-13), Stability, electronic band structure, magnetic, optical and thermoelectric properties of CoXCrZ (X = Fe, Mn and Z = Al, Si) and FeMnCrSb quaternary Heusle, Chinese Journal of Physics, Vol:81, Issue:81, pages:303-324, Elseier

We carried out a theoretical study on hexahalometallate single crystals X2SnBr6 (X = Rb, Cs) with the density functional theory framework, using generalized gradient approximation of the Perdew, Burke, and Ernzerhof and Heyd–Scuseria–Ernzerhof hybrid functional. The lattice constant of the compounds Cs2SnBr6 and Rb2SnBr6 is consistent with the experimental data currently available, with an uncertainty of 0.04% and 0.07%, respectively. For the first time, the elastic moduli of Cs2SnBr6 at equilibrium and under pressure effect were estimated. When fitted to the Birch–Murnaghan equation of state, the bulk modulus of Cs2SnBr6 and Rb2SnBr6 obtained using the generalized gradient approximation optimization is closer to the experimental one. The interatomic distances of Cs2SnBr6 are greater than those of Rb2SnBr6, because these distances are proportional to the radius of Cs (1.73 Å) and Rb (1.64 Å). The direct band gap Γ–Γ of 1.272 eV and 1.1019 eV for, respectively, Cs2SnBr6 and Rb2SnBr6 explains their semiconducting character. The Sn-s state dominates in the conduction band minima, indicating that Sn and Br are in ionic connection in both Cs2SnBr6 and Rb2SnBr6. © 2023 Polish Academy of Sciences. All rights reserved.

Citation

MohamedAmine GHEBOULI , , (2023-01-01), Structural, Elastic, Electronic and Optical Properties Study of Hexahalometallate Single Crystals X2SnBr6 (X = Rb, Cs), ACTA PHYSICA POLONICA A, Vol:143, Issue:1, pages:1-9, POLONIA

The functionals mBJ-LDA and mBJ-GGA result in high band gaps. BiGaO3 contains covalent bonds due to the mixing of O 2p states with the Bi and Ga s,p states. The Bi breadth PDOS was obviously less in the valence band region compared to Ga and O, with fewer peaks than there were for Ga and consequently Ga-O hybridization is more powerful than Bi-O hybridization. All optical spectra obtained by using mBJ-GGA and EV-GGA approaches have the same profile. At the same energy as the indirect M-X band gap values of 2.24 and 2.56 eV for EV-GGA and mBJ-GGA, the imaginary component reaches non-zero magnitude. The increase in temperature from 300 to 800 K reduces the Seebeck coefficient in BiGaO3 from (3000 to 1500) μV/K. As p-type and n-type ZT have similar values, BiGaO3 has the same thermoelectric efficiency whether it is p-type or n-type.

Citation

MohamedAmine GHEBOULI , , (2022), The impact of functionals on BiGaO3 structural, electronic, optical and thermoelectric properties, Chemical Physics Impact, Vol:5, Issue:5, pages:100110, sciencedirect

Some physical properties of hexahalometallate K2XBr6(X = Se, Pt) were computed in the zinc blend structure using GGA-PBESOL. The cell constant of K2SeBr6 and K2PtBr6 is consistent to the experiment value quoted in the literature, where the error is 0.95% and 1%. K2SeBr6 and K2PtBr6 present covalent bonding, high anisotropy and are ductile. The elastic constants of K2SeBr6 and K2PtBr6 are significantly smaller due to their larger reticular distances, lower Coulomb forces and then they are soft and damage tolerant. The interatomic separation is greater in K2SeBr6 than in K2PtBr6, hence the Coulomb interaction in K2PtBr6 is greater than that of K2SeBr6. The internal coordinate of Br atom in K2PtBr6 is lower than that of the same atom in K2SeBr6, and this can be explained by the fact that it is inversely proportional to the atom radius of Se and Pt. There are two major plasmonic processes, with intensities 3.7 and 1.35 located around 53.5 nm and 72.8 nm for K2SeBr6 and K2PtBr6.

Citation

MohamedAmine GHEBOULI , , (2022), Ab-initio Study of structural, elastic, electronic and optical properties of hexahalometallate single crystals K2XBr6(X = Se, Pt), Scientific Reports, Vol:12, Issue:481, pages:8345, Springer

The tunability of the physical parameters of ZnS1-xOx alloy in the wurtzite phase makes this semiconductor potentially useful as an absorbent layer and antireflection coating. A deviation of the bulk modulus from Vegard’s law is observed in ZnS1-xOx alloy. Based on the density functional theory as implemented in the Wien2k code under the virtual crystal approximation, the lattice constant, bulk modulus and band gap have been calculated with both GGA and the modified Becke-Johnson potential (mBJ). The ternary ZnS1-xOx alloy becomes more stable with the increase in the oxygen content x. The in-plane and out-of-plane imaginary components of the dielectric function attain non-zero magnitude at energy identical to the fundamental band gap value. The intense peaks in the in-plane and out-of-plane dielectric function located at 6.5 eV and 7.75 eV suggest inter band transition, and no photon emission in this material. ZnS1-xOx absorbs ultraviolet light in the range 4 eV–10 eV, which validates its candidature for optical and photovoltaic devices. The refractive index is more important when photons move through the material and when bonds between atoms are covalent. The anisotropic optical pa- rameters, the fundamental band gap range (2.7–3.7 eV) and absorption of extreme ultraviolet light make ZnS1- xOx alloy as windows, lenses and absorber material

Citation

MohamedAmine GHEBOULI , , (2022), Effect of oxygen content on structural and optoelectronic properties of ZnS1- xOx alloy in the wurtzite structure, Solid State Communications, Vol:354, Issue:354, pages:114897, sciencedirect

ome fundamental physical properties of BiGaO 3 were investigated under pressure and temperature effect using GGA and LDA. The effect of orientation on Debye temperature and sound wave velocities were estimated from elastic constants. The bulk modulus value of BiGaO 3 is a sign of its high hardness, because it is linked to an isotropic deformation. BiGaO 3 is a semiconductor and ductile material, with covalent (Ga–O) and ionic Bi-O bonding. The optical transitions were observed when electrons pass from the top of the valence band (O-2p) to the bottom of the conduction band (Ga-4p or Bi-6p). The thermodynamic parameters were determined in temperature and pressure ranging from 0 to 1800 K and 0 to 50 GPa

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MohamedAmine GHEBOULI , , (2022), Prediction study of the structural, elastic, electronic, dynamic, optical and thermodynamic properties of cubic perovskite BiGaO3, Bulletin of Materials Science, Vol:45, Issue:139, pages:124, Springer

The structural, elastic, electrical, and thermodynamic characteristics of Fe2Hf cubic and hexagonal phases with space group Fd-3m and P63/mmc are presented using the generalized gradient approximations. The k-points mesh density and plane-wave energy cut-off accomplish the energy convergence. The computed equilibrium parameters are closer to the theoretical data. The elastic tensor and crystal anisotropy of ultra- incompressible Fe2Hf are computed in a wide pressure range. The isothermal and adiabatic bulk modulus, as well as the heat capacity of Fe2Hf is successfully calculated utilizing the quasi-harmonic Debye Model. The Fd-3m and P63/mmc Fe2Hf structures are stable in the studied pressure range

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MohamedAmine GHEBOULI , , (2022), Density functional prediction of the structural, elastic, electronic, and thermodynamic properties of the cubic and hexagonal (c, h)-Fe2Hf, Modeling and simulation in metallurgical and materials engineering, Vol:28, Issue:2, pages:172, Springer

The C 14H 12Br 2S3 molecule has twofold imposed crystallographic symmetry in the solid state. 2C14H 12Br2 S3Bis (2-Bromobenzyl) trisulfide in the orthorhombic structure with space group P2 12 12 is described and compared with other similar compounds. The structural, electronic, and optical properties of the anhydrous orthorhombic 2C14H 12Br2 S3 Bis (2- Bromobenzyl) trisulfide crystals were treated within LDA/CA-PZ, GGA/PBE and GGA/PW91 approaches. The lattice parameters calculated with LDA/CA-PZ (a ¼ 12.651 A, b ¼ 12.881 A and c ¼ 4.992 A) are in better agreement with experimental values, where the error is 0.90%, 1.14%, and 4.79% for a cutoff energy 240 eV. This calculation shows the usual trends, where the GGA/PBE and GGA/PW91 functional overestimate the lattice constant, unlike the LDA/ CA-PZ. The C 14H 12Br2 S3 molecule has a large indirect band gap Z/G of 3.4498 eV and 3.5319 eV computed within LDA/CA-PZ and GGA/PBE approaches. The hybridization in the upper valence band between S: p, B: p and C: p, translates their covalent bonding. The Mulliken population charges show the zwitterionic state of the C14H 12Br 2S3 molecule.

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MohamedAmine GHEBOULI , , (2022), Structural, electronic and optical properties of the anhydrous orthorhombic 2C14 H12 Br2S 3Bis (2-Bromobenzyl) trisulfide crystals, Journal of Materials Research and Technology, Vol:18, Issue:18, pages:396, sciencedirect

Using generalized gradient approximation (GGA) and local density approxima-tion (LDA), the phase stability, electronic, and optical characteristics of BiGaO3inthePcca,R3c, andPm-3mphases are examined. The structural phase transitioncan be caused by the few soft modes betweenFandZpoints in theR3cphase.Because it is coupled to isotropic deformation, the bulk modulus of BiGaO3is anindicator of its high hardness. When electrons travel from the top of the valenceband (O-2p) to the bottom of the conduction band (Ga-4por Bi-6p), opticaltransitions are detected. The pyroxenePccaphase of BiGaO3is the most stable,according to GGA–Perdew–Burke–Ernzerhof (PBE) total energy calculations. At5 GPa, the phase change from thePccato theR3cstructure occurs. Because ofthe smaller reticular lengths and higher Coulomb forces, the elastic constants ofBiGaO3are quite significant

Citation

MohamedAmine GHEBOULI , , (2022), Phase Stability, Electronic, and Optical Properties in Pcca, R3c, and Pm-3m Phases of BiGaO3 Perovskite, basic solid state physics, Vol:259, Issue:259, pages:2200042, wily

Cet ouvrage qui comprend des exercices corrigés a été réalisé dans le but de faciliter la compréhension de la structure de la matière et les liaisons chimiques. Ce document est destiné principalement aux étudiants de la première année des filières Sciences de la Matière (SM), Sciences Techniques (ST), et Sciences de la Nature et de la Vie (SVI). Cette édition d'exercices corrigés permet aux étudiants de ces filières d’acquérir une méthodologie adéquate pour résoudre les problèmes de la chimie de l’atome. Ce manuscrit se compose de cinq parties, où on étudie principalement la structure de l'atome, les modèles quantique et ondulatoire de l'atome de Bohr, la classification périodique et la structure électronique des éléments ainsi que leurs propriétés et enfin les liaisons chimiques entre atomes et molécules. Chaque chapitre comprend une série d’exercices choisie pour son intérêt et sa diversité. On reporte aussi le corrigé détaillé de cette série afin que les étudiants puissent assimiler le cours de cette matière. On propose dans le premier chapitre des exercices de connaissances générales sur la structure de l’atome, sur les isotopes et les défauts de masse. Le second chapitre est consacré au calcul des différents paramètres de l’atome d’hydrogène et des ions hydrogénites selon le modèle de Bohr. L'étude des différentes séries spectrales de l’atome d’hydrogène est également bien détaillée. Dans le troisième chapitre, on traite le modèle ondulatoire de l’atome qui comprend la relation de Louis De Broglie, l'équation de Schrödinger, les fonctions d’ondes et les orbitales atomiques. On détermine aussi les structures électroniques des éléments en utilisant les règles de remplissage des électrons dans les différentes couches et sous-couches de l’atome. Les exercices que contient le chapitre quatre servent à déterminer la structure électronique d’un atome et son numéro atomique suivant son classement dans le tableau périodique. Ces exercices permettent aussi de trouver le groupe ou la période auxquels appartient l’atome. Le dernier chapitre traite des exercices d'application sur les différentes liaisons chimiques possibles entre les atomes et molécules. Mon souhait est que ce modeste travail améliore l'encadrement et la formation dans notre Université et qu'il sera d'une grande importance à nos étudiants pour acquérir une base solide en chimie de la matière.

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MohamedAmineGHEBOULI , ,(2021); بنية المادة,جامعة محمد بوضياف,

We calculated equilibrium lattice constant , bulk modulus , pressure derivative and bond lengths and using both GGA and LDA approaches for ScF3. We predict the elastic moduli using GGA and LDA functional. The ScF 3 is elastically and dynamically stable in the pressure range 0–38 GPa. The Young’s modulus, shear modulus, linear compressibility and Poisson’s ratio have a maximum value and another minimum in each direction explaining their anisotropy. The indirect R–X band gap value of 6.139 eV and the electronic DOS indicate the insulator character in ScF3. The predicted GGA and LDA values of elec- tron effective masses for ScF3 are 1.604 and 1.703, respectively. The longitudinal and transversal optical phonon frequencies ωL0 and ωT0 at R point for ScF3 are 725.69 and 588.5 cm–1. The volumetric thermal expansion coef- ficient, the constant volume and pressure heat capacities and entropy at zero pressure and 300 K are 5.14 × 105 K–1 , 83.86, 86.54, and 77.48 J mol –1 K–1 for ScF3. The edge of the optical absorption located at 31.53 nm is caused by V1−C1 transition at X point, which corresponds to the indirect band gap R–X.

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MohamedAmine GHEBOULI , , (2021), Predicted Structural, Elastic, Electronic, Lattice Dynamic, Thermodynamic and Optical Properties of Cubic SсF3 from First-Principles Calculations, STRUCTURE OF MATTER AND QUANTUM CHEMISTRY, Vol:95, Issue:43, pages:S296–S306, Springer

We focus on detailed investigation of structural, elastic, electronic, and optical properties of inorganic complex chloride and bromide CsInCl3 and CsInBr3 in zinc blende structure within GGA and LDA. The lattice constant for CsInCl3 and CsInBr3 computed with GGA approach is closer to experimental value, where the estimated error is 0.2% and 0.28%. Elastic moduli at equilibrium and under pressure effect for CsInCl3 and CsInBr3 are studied for the first time. CsInCl3 and CsInBr3 are elastically stable, ductile, show lower hardness and have dominantly covalent bonding character. Band structure of CsInCl3 and CsInBr3 computed with GGA (LDA) indicate an indirect band gap L-X: 1.583 eV (1.186 eV) and L-W: 0.831 eV (0.75 eV) which traduce their semiconducting character. We report the predicted GGA and LDA electron and hole effective masses and for CsInCl3 and CsInBr3. The Cs: p site is empty in the first conduction band, consequently, transitions occur from Cl: p (Br: p) state to Cs: p site. Lattice constant and bond lengths of CsInX3 (X = Cl, Br) are proportional to the radius of X atom. The anisotropy is more pronounced in the LDA approach for CsInCl3 and CsInBr3. The indirect band gap L-X becomes L-W at about 0.5 GPa for inorganic complex chloride CsInCl3, while CsInBr3 has a tendency to the metallic character.

Citation

MohamedAmine GHEBOULI , , (2021), Predicted structural, elastic, electronic and optical properties of inorganic complex chloride and bromide CsInCl3 and CsInBr3, Materials Science in Semiconductor Processing, Vol:135, Issue:135, pages:106033, sciencedirect

We studied the structural, elastic, electronic, dynamic and optical properties of scandium and yttrium nitrides in the zinc blend structure. The GGA, LDA and GGA-PBESOL ap- proaches, as well as the HSE hybrid functional, were used in the representation of the electronic exchange and correlation effects. The lattice constant, the bulk modulus and its pressure derivative calculated in the HSE hybrid approach are predictions. The elastic constants and B/G ratio infer that ScN and YN are elastically stable and ductile in nature. ScN and YN in the zinc blend structure show an isotropic linear compressibility and anisotropic Young's modulus, shear modulus and Poisson's ratio. The anisotropy and hardness in ScN and YN compounds are more pronounced in the LDA approach. The XeX (WeW) direct band gap in scandium (yttrium) nitride translates its semiconductor char- acter in the zinc blend structure. The N: p orbit and small contribution of Sc: d (Y: d) site are responsible to the optical modes, while Sc: d (Y: d) site and small contribution of N: p orbit are the sign of acoustical modes. The absorption peaks are assigned to photo transitions energies from maximum valence band to minimum conduction band.

Citation

MohamedAmine GHEBOULI , , (2021), First-principles calculations to investigate structural, elastic, electronic, lattice dynamic and optical properties for scandium and yttrium nitrides in zinc blend structure, Journal of Materials Research and Technology, Vol:14, Issue:14, pages:1958, sciencedirect

We report the performance of glass/Mo/CuInSSe(CISSe)/(Zn2SnO4, CdS, SnS2)/ZnO thin films structures using solar cell capacitance simulator (SCAPS). Thin films solar cells with CuInSSe absorber layer reduce the cost and have comparable performance parameters with the conven- tional ones. The temperature effect on efficiency and fill factor is less noticeable in solar cell with Zn2SnO4 buffer layer. The average temperature gradient of CdS, SnS2 and Zn2SnO4 based cells value is -0.317 %/K, -0.533 %/K and -0.539 %/K. An efficiency of 18.53 % has been achieved with Zn2SnO4 buffer for Voc, Jsc and FF of 0.5153 V, 45.4 mAcm

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MohamedAmine GHEBOULI , , (2021), Effect of nature buffer, CISSe thikness layers and temperature on solar cells performance using Scaps-1D simulation program, Optik, Vol:241, Issue:241, pages:166203, sciencedirect

We have calculated the bond lengths , , , , , , and single-crystal elastic stiffness constants, Cij and polycrystalline elastic moduli at different pressures by using GGA-PBE, GGA-PBESOL and LDA approach for cubic YF3. Yttrium fluoride is found to be elastically stable in the pressure range 0–40 GPa. Shear modulus, linear compressibility and Poisson's ratio have maximum and minimum values along with different crystallographic directions, which explain their predicted anisotropy. The direct Γ-Γ band gap value 5.082 eV indicates towards the insulating character of YF3. The broad band gap is a sign that this compound should function as an emission center. We predicted the first and second-order pressure coefficients of direct and indirect band gaps using the GGA-PBE, GGA-PBESOL and LDA approaches. The estimated volumetric thermal expansion coefficient, constants volume and constant pressure heat capacities and entropy at zero pressure and 300 K are 1.66 × 105 K−1, and 83.59 mol-1 K−1, respectively. The edge of the optical absorption is located at 48.5 nm which is caused by the V1−C1 transition at the Γ point in the Brillouin zone that corresponds very well to the direct band gap at Γ- Γ.

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MohamedAmine GHEBOULI , , (2021), Electronic band structure, elastic, optical and thermodynamic characteristic of cubic YF3: An ab initio study, Optik, Vol:239, Issue:239, pages:166680, sciencedirect

We report structural, elastic, electronic, dynamical and optical properties of beryllium selenide in zinc blend and NiAs phases. The zinc blend structure is the most stable at room temperature and equilibrium hydrostatic pressure. The HSE hybrid functional underestimates the lattice parameters compared to the GGA-PBE and LDA, but gives a fundamental gap closer to its experiment value. We derive bulk modulus, shear modulus, Young's modulus and Poisson's ratio using Voigt, Reuss and Hill approximations. Computed elastic constants in NiAs structure are predictions. Waves velocities for beryllium selenide in zinc blend (NiAs) phase along [100], [110] ([100], [110], [111]) directions are predictions. The indirect band gap Γ-X (2.852 eV) and Γ-K (0.536 eV) for BeSe in zinc blend and NiAs structures translates the semiconductor nature. Hybridization occurs between Se: p and Be: s states at the top of the valence band and traduces the covalent bonding character. The first conduction band is quite wide in both structures, where the contribution is due to Se: p, Se: s and Be: s sites. The electronic transition occurs from Se: p orbital of valence band to Be: s site of conduction band. Absorption peaks are attributed to the photo transition energies from the maximum valence band to the minimum conduction band under ultra violet light irradiation.

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MohamedAmine GHEBOULI , , (2021), Study of structural, elastic, electronic, dynamical and optical properties of beryllium selenide (BeSe) semiconductor in zinc blend and NiAs phases, Physica B: Condensed Matter, Vol:610, Issue:610, pages:412858, sciencedirect

The GGA functional PW91 were used in order to predict the structural, electronic, optical and elastic properties of α and β of d- Glucose. Such compounds, in their solid form, are widely used in chemical and pharmaceutical industry. The pure crystalline forms of glucose α-d-glucose and β-d-glucose have the same space group (McDonald and Beevers, 1950) [1]. We note that despite the fact that the two compounds have the same space group, upon cooling, the interatomic distances change and a new compound occurs. On the other hand, the cooling also influences the physical properties (structural, elastic, electronic and optical properties). The objective of this paper is associated with the control of the physical states of molecular materials when they are subjected to polymorphic changes. The laws and physical parameters that govern these transformations remain fundamentally misunderstood.

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MohamedAmine GHEBOULI , , (2021), Predictive physical study of two different crystalline forms of glucose, Biochemistry and Biophysics Reports, Vol:25, Issue:25, pages:100923, sciencedirect

We expose various physical parameters of binary compound BeSe in the stable zinc blend and NiAs structures using the functional HSE hybrid, GGA-PBE, and LDA. We deduce elastic constants, mechanical parameters, and wave velocities according to different orientations. BeSe semiconductor has
-X (2.852 eV) and
-K (0.536 eV) bandgap in zinc blend and NiAs structures. Electrons transit from Se-p site to the Be-s state and show covalent bonding. Optical absorption peaks result from electronic transitions under ultraviolet light irradiation

Citation

MohamedAmineGHEBOULI , ,(2021); Contribution to the Calculation of Physical Properties of BeSe Semiconductor,,IntechOpen

Special quasi-random structure (SQS) was used to investigate the structural, electronic, and optical characteristics of the binary and ternary beryllium chalcogenide alloys. The computations were performed using the pseudopotential technique. The GGA-WC scheme was applied to study the structural and optical features of these present alloys, while the HSE06 hybrid functional was used to correct the underestimation of the electronic band structure. The optimized lattice constants and bulk modulus demonstrate a non-linear tendency with increasing x concentration. The phase transition may occur for all ternary alloys at x  = 0.5 with the orthorhombic assumed crystal system. The ternary alloys of have an indirect band gap, while manifest a metallic demeanor using HSE06 formalism. The optical spectra were computed and discussed in detail. Furthermore, the thermodynamic stability of the studied compounds was examined using the miscibility critical temperature.

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MohamedAmine GHEBOULI , Mohammed M.Obeid, R.Khenata, Majid M.Shukur, Shaker J.Edrees, Shakeel Ahmad, A. Bouhemadou, Hamad RahmanJappor, , (2019), Electronic band structure, thermodynamics and optical characteristics of BeO1−xAx(A = S, Se, Te) alloys: Insights from ab initio study, Chemical Physics, Vol:526, Issue:, pages:110414, sciencedirect

We studied the ternary acetylides A2MC2 (A = Na, K) and (M = Pb, Pt) with trigonal structures by using the density functional theory (DFT) as implemented in the CASTEP code. The calculated lattice parameters and atomic fractional coordinates were in agreement with previous calculations and experimental data. A set of isotropic elastic parameters and related properties, namely the module and shear moduli, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature were numerically estimated in the frame work of the Voigt-Reuss-Hill approximation. The absorption, energy-loss and dielectric function were calculated. We studied the main contribution to the optical spectra from the transition from the top four valence bands towards the lower three first one of conduction based on the electronic structures.

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MohamedAmine GHEBOULI , Messaoud Fatmi, Tayeb CHIHI, Brahim Ghebouli, , (2019), Study of the Structural, Elastic, Electronic and Optical Properties of the Ternary Acetylides A2MC2 (A = Na, K) and (M = Pb, Pt), Journal- Korean Physical Society, Vol:75, Issue:9, pages:678-684, Springer

We derived the chemical compositions and the micro hardness of the two studied steels Fe20Mn5Cr and Fe9S28Mn. The contamination of these two compounds by oxygen gives the series M2O3 (M = Fe, Cr, Al). Rhombohedral crystal structure of these compounds was determined by means of the X-rays diffraction. First principles calculations were performed to investigate structural, elastic and mechanical properties of M2O3 (M = Fe, Cr, Al) compounds at equilibrium pressure. Fe2O3 and Cr2O3 are classified as ductile materials, while Al2O3 is brittle. The Debye temperature, the elastic wave velocities and the integration of elastic wave velocities in various directions of the single crystal were obtained. All these compounds are elastically and chemically stable. The calculated elastic constants are in good agreement with the experiment values in the approximation of the gradient generalized for the correlation and exchange potential. We calculated the partial and total densities of states PDOD and TDOS for M2O3 (M = Fe, Cr, Al) compounds. As a result, electronic bands, DOS at the Fermi level, were obtained for the first time especially for Fe2O3 and Cr2O3.

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MohamedAmine GHEBOULI , Tayeb CHIHI, Messaoud Fatmi, Brahim GHEBOULI, , (2019), Structural, elastic, thermoelastic and electronic properties of M2O3 (M = Cr, Fe, Al) compounds: Experimental and theoretical study, Results in Physics, Vol:12, Issue:, pages:725, Sciencedirect.

We studied the ternary acetylides A2MC2 (A = Na, K) and (M = Pb, Pt) with trigonal structures by using the density functional theory (DFT) as implemented in the CASTEP code. The calculated lattice parameters and atomic fractional coordinates were in agreement with previous calculations and experimental data. A set of isotropic elastic parameters and related properties, namely the module and shear moduli, Young’s modulus, Poisson’s ratio, average sound velocity and Debye tem- perature were numerically estimated in the frame work of the Voigt-Reuss-Hill approximation. The absorption, energy-loss and dielectric function were calculated. We studied the main contribution to the optical spectra from the transition from the top four valence bands towards the lower three first one of conduction based on the electronic structures

Citation

MohamedAmine GHEBOULI , , (2019), Study of the Structural, Elastic, Electronic and Optical Properties of the Ternary Acetylides A2MC2 (A = Na, K) and (M = Pb, Pt), kournal of the Korean Physical Society, Vol:75, Issue:9, pages:678, Springer

Special quasi-random structure (SQS) was used to investigate the structural, electronic, and optical character- istics of the binary and ternary beryllium chalcogenide alloys. The computations were performed using the pseudopotential technique. The GGA-WC scheme was applied to study the structural and optical features of these present alloys, while the HSE06 hybrid functional was used to correct the underestimation of the electronic band structure. The optimized lattice constants and bulk modulus demonstrate a non-linear tendency with increasing x concentration. The phase transition may occur for all ternary alloys at x = 0.5 with the orthorhombic assumed crystal system. The ternary alloys of BeO1−xAx (A = S, Se) at 0.5 x 1 have an indirect band gap, while BeO1−xTex0.5 x 1 manifest a metallic demeanor using HSE06 formalism. The optical spectra were computed and discussed in detail. Furthermore, the thermodynamic stability of the studied compounds was examined using the miscibility critical temperature.

Citation

MohamedAmine GHEBOULI , , (2019), Electronic band structure, thermodynamics and optical characteristics of BeO1−xAx(A = S, Se, Te) alloys: Insights from ab initio study, Chemical Physics, Vol:526, Issue:526, pages:110414, sciencedirect

This study investigated the effect of aging on the precipitation and kinetics of second-phase Mg17Al12 in AZ91 magnesium alloy (Mg-9 wt% Al-1 wt% Zn), using X-ray diffraction, microhardness measurements, and differential scanning calorimetric analysis (DSC). With the last instrument, the all samples were heated from room temperature to 400 °C, at heating rates of 10–30 °C/min. The results were supplemented by measuring the average of activation energies, using isothermal treatments by Johnson–Mehl–Avrami (JMA) methods and by non-isothermal treatments using Ozawa, Boswell, Kissinger, Mahadevan, Augis and Bennett methods, were around 67.18 and 62.02 kJ/mol. The frequency factor k0 calculated by the isothermal treatment is equal to 1.24 109 s−1. In non-isothermal treatment, the numerical factor m and the Avrami parameter n is estimated to be approximately equal to 3 and 2.79 respectively. This value corresponding that the bulk nucleation with a constant number of nuclei was dominant in three-dimensional (polyhedron) controlled by interface reaction

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AMAR Djemli , Ameur Ouali , MohamedAmine GHEBOULI , Hocine BELHOUCHET , Fatmi messaoud, Tayab Chihi, , (2018-07-20), Heat treatment and kinetics of precipitation of β-Mg17Al12 phase in AZ91 alloy, Results in Physics, Vol:10, Issue:2018, pages:693-698, Elsevier

The lead free halides double perovskites show a particular interest in the conception of perovskites solar cells. We predicted the lattice constant and the atomic Wycko position of these lead free halide double perovskites Cs2AgBiX6 (X = Br, Cl) under pressure effect. The alloying ability of crystal, elastic constants and related parameters, electronic and optical properties have been studied using pseudo potential plane wave method based on the density functional theory. The investigated lead free halide double perovskites Cs2AgBiX6 (X = Br, Cl) show a weaker resistance to compression along the a-axis. This result also proves the existence of a directional bonding between atoms and a weaker resistance to compression along the a-axis The band structure indicates that Cs2AgBiX(X = Br, Cl) are X–L indirect gap semiconductors. Our computed bulk modulus and its pressure derivative of double perovskites Cs2AgBiX6 (X = Br, Cl) are predictions. The calculated elastic constants of Cs2AgBiX6 (X = Br, Cl) at equilibrium and under pressure effect are predictions.

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MohamedAmine GHEBOULI , Tayeb CHIHI, Brahim GHEBOULI, Messaoud Fatmi, , (2018), Study of the structural, elastic, electronic and optical properties of lead free halide double perovskites Cs2AgBiX6(X = Br, Cl), Chinese Journal of Physics, Vol:56, Issue:1, pages:323, Sciencedirect.

First principles calculations are applied in the study of FeMP (M = Ti, Zr, Hf) compounds. We investigate the structural, elastic, mechanical and electronic properties by combining first-principles calculations with the CASTEP approach. For ideal polycrystalline FeMP (M = Ti, Zr, Hf) the shear modulus, Young’s modulus, Poisson’s ratio, elastic anisotropy indexes, Pugh’s criterion, elastic wave velocities and Debye temperature are also calculated from the single crystal elastic constants. The shear anisotropic factors and anisotropy are obtained from the single crystal elastic constants. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal.

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MohamedAmine GHEBOULI , A.Tanto, Tayeb chihi, Mounir Reffas, Messaoud Fatmi, Brahim GHEBOULI, , (2018), Prediction study of structural, elastic and electronic properties of FeMP (M = Ti, Zr, Hf) compounds, Results in Physics, Vol:9, Issue:, pages:763, Sciencedirect.

This study investigated the effect of aging on the precipitation and kinetics of second phase Mg17Al12 in AZ91 magnesium alloy (Mg-9 wt% Al-1 wt% Zn), using X-ray diffraction, microhardness measurements and differential scanning calorimetric analysis (DSC). With the last instrument, the all samples were heated from room temperature to 400 °C, at heating rates of 10–30 °C/min. The results were supplemented by measuring the average of activation energies, using isothermal treatments by Johnson–Mehl–Avrami (JMA) methods and by non-isothermal treatments using Ozawa, Boswell, Kissinger, Mahadevan, Augis and Bennett methods, were around 67.18 and 62.02 kJ/mol. The frequency factor k0 calculated by the isothermal treatment is equal to 1.24 109 s−1. In non-isothermal treatment, the numerical factor m and the Avrami parameter n is estimated to be approximately equal to 3 and 2.79 respectively. This value corresponding that the bulk nucleation with a constant number of nuclei was dominant in three-dimensional (polyhedron) controlled by interface reaction.

Citation

MohamedAmine GHEBOULI , Messaoud Fatmi, A. Djemli², A. Ouali, Tayeb Chihi, H.Belhouchet, , (2018), Heat treatment and kinetics of precipitation of β-Mg17Al12 phase in AZ91 alloy, Results in Physics, Vol:10, Issue:, pages:693, Sciencedirect.

In this paper, we present a detailed theoretical investigation on the structural, elastic, electronic and optical properties of the perovskite oxides SrThO3 and SrZrO3 by using the pseudo-potential plane wave (PP-PW) method. The computed lattice constants of SrXO3 (X = Th and Zr) are in excellent agreement with the available experimental data. SrThO3 and SrZrO3 are direct (Γ–Γ) and indirect (Γ–R) band gap semiconductors, respectively. Under pressure effect a crossover between the indirect band gap (R–Γ) and the direct band gap (Γ–Γ) curves occurs at about 35 GPa for SrZrO3, resulting in the energy minimum of direct gap (Γ–Γ) for this compound. The covalence in the Zr–O and Th–O bonds arises due to the hybridization between O–p and Zr–d (Th–d) states. Under pressure effect, the threshold energy becomes slightly greater (smaller) for SrZrO3 (SrTO3) for 3.21 (2.28) eV and the main peaks are shifted towards higher energies. Although the positions of all peaks shifted under pressure, they still have the same type as those at zero pressure, with decreasing the intensity of the main peaks.

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MohamedAmine GHEBOULI , Tayeb CHIHI, F. Dahman, Brahim GHEBOULI, Messaoud Fatmi, Tarek Seddik, A. Abdiche, Rabah Khenata, , (2018), Structural, elastic and optoelectronic properties of Sr-based perovskite-type oxides SrXO3 (M = Th, Zr) via first-principles calculations, Chinese Journal of Physics, Vol:56, Issue:4, pages:1515, Sciencedirect.

The structural, electronic, optical and thermodynamic properties of SrxCa1−xO, BaxSr1−xO and BaxCa1−xO ternary alloys in NaCl phase were studied using pseudo-potential plane-wave method within the density functional theory. We modeled the alloys at some selected compositions with ordered structures described in terms of periodically repeated supercells. The dependence of the lattice parameters, band gaps, dielectric constants, refractive indices, Debye temperatures, mixing entropies and heat capacities on the composition x were analyzed for x = 0, 0.25, 0.50, 0.75 and 1. The lattice constant for SrxCa1−xO and BaxSr1−xO exhibits a marginal deviation from the Vegard's law, while the BaxCa1−xO lattice constant exhibits an appreciable upward bowing. A strong deviation of the bulk modulus from linear concentration dependence was observed for the three alloys. The microscopic origins of the gap bowing were detailed and explained. The composition dependence of the dielectric constant and refractive index was studied using different models. The thermodynamic stability of these alloys was investigated by calculating the phase diagram. The thermal effect on some macroscopic properties was investigated using the quasi-harmonic Debye model. There is a good agreement between our results and the available experimental data for the binary compounds which may be a support for the results of the ternary alloys reported here for the first time.

Citation

MohamedAmine GHEBOULI , ,(2018), Structural, electronic, optical and thermodynamic properties of SrxCa1−xO, BaxSr1−xO and BaxCa1−xO alloys,4 TH INTERNATIONAL CONFERENCE ON ADVANCES IN MECHANICAL ENGINEERING,Yildiz university

Ce polycopié est destiné aux étudiants de première année du système Licence-Master-Doctorat (L.M.D), spécialité : Sciences et Technologie (S.T) Il comporte un rappel de cours et des exercices résolus sur les différents chapitres du module chimie 2 (thermodynamique). Le cours permet d’acquérir certaines notions fondamentales en thermodynamique facilitant ainsi une meilleure maitrise des concepts fondamentaux appliqués dans le domaine d’ingénierie thermique. Le polycopié est réparti en cinque chapitres : Le premier chapitre: Généralités sur la thermodynamique avec un rappel de notions mathématiques ainsi que quelques définitions en rapport avec la thermodynamique en général. Le deuxième chapitre : Température, Chaleur, travail et Calorimétrie Le troisième chapitre : Enoncé du premier principe de la thermodynamique. Le quatrième chapitre : Applications du premier principe en thermochimie et le cinquième chapitre : Second principe de la thermodynamique.

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MohamedAmineGHEBOULI , ,(2018); Thermodynamique,Mohamed Boudiaf - M'sila -,

Cet ouvrage qui comprend des exercices corrigés a été réalisé dans le but de faciliter la compréhension de la structure de la matière et les liaisons chimiques. Ce document est destiné principalement aux étudiants de la première année des filières Sciences de la Matière (SM), Sciences Techniques (ST), et Sciences de la Nature et de la Vie (SVI). Cette édition d'exercices corrigés permet aux étudiants de ces filières d’acquérir une méthodologie adéquate pour résoudre les problèmes de la chimie de l’atome. Ce manuscrit se compose de cinq parties, où on étudie principalement la structure de l'atome, les modèles quantique et ondulatoire de l'atome de Bohr, la classification périodique et la structure électronique des éléments ainsi que leurs propriétés et enfin les liaisons chimiques entre atomes et molécules. Chaque chapitre comprend une série d’exercices choisie pour son intérêt et sa diversité. On reporte aussi le corrigé détaillé de cette série afin que les étudiant peuvent assimiler le cours de cette matière. On propose dans le premier chapitre des exercices de connaissances générales sur la structure de l’atome, sur les isotopes et les défauts de masse. Le second chapitre est consacré au calcul des différents paramètres de l’atome d’hydrogène et des ions hydrogènoïdes selon le modèle de Bohr. L'étude des différentes séries spectrales de l’atome d’hydrogène est également bien détaillé. Dans le troisième chapitre, on traite le modèle ondulatoire de l’atome qui comprend la relation de Louis De Broglie, l'équation de Schrödinger, les fonctions d’ondes et les orbitales atomiques. On détermine aussi les structures électroniques des éléments en utilisant les règles de remplissage des électrons dans les différentes couches et sous-couches de l’atome. Les exercices que contient le chapitre quatre servent à déterminer la structure électronique d’un atome et son numéro atomique suivant son classement dans le tableau périodique. Ces exercices permettent aussi de trouver le groupe ou la période auxquels appartient l’atome. Le dernier chapitre traite des exercices d'application sur les différentes liaisons chimiques possibles entre les atomes et molécules. Mon souhait est que ce modeste travail améliore l'encadrement et la formation dans notre Université et qu'il sera d'une grande importance à nos étudiants pour acquérir une base solide en chimie de la matière.

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MohamedAmineGHEBOULI , ,(2018); Thermodynamique,جامعة محمد بوضياف,

Based on the density functional theory as implemented in the Abinit code under the virtual crystal approximation, the lattice constant, bulk modulus, elastic constants, gap energies, electron effective mass, the dielectric constants and born effective charge in In1−x−yAlxGayAs have been calculated with both GGA and LDA in the range 0≤y≤0.9801. The optical and acoustical phonon frequencies, Fröhlich coupling parameter, deformation energy and polaron effective mass are calculated and their dependence on the Ga content is examined. For AlAs, our results are in reasonable agreement with the known data in the literature; while for other contents our treatments are predictions.

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MohamedAmine GHEBOULI , ,(2018), First-principles study on stability, energy gaps, optical phonon and related parameters of In1-x-yAlxGayAs alloys,Synergistic Approaches in Solar Energy Conversion conference,saudi arabia

We studied the profiles of the micro hardness in the nuances 9SMn28, 42CrMo4 and CK45, which have a rapid decline to the depth 0.1 mm, and then slowly decrease to the value of the characteristic of the casting material. The surface layer contains mostly the iron nitrides phases FeyN (y = 1, 2, 3, 4). We use first principles to study the electronic and magnetic properties of some structural phases. We calculated the lattice parameters of all the compounds; our results show good agreement with other calculations. The estimated formation energies first show a decrease then an increase with the nitrogen content. The contribution of the PDOS is due to the Fe-3d and N-2p states in Fe(1–4)N. We used experimental and theoretical studies to determine all of the phases existing in a nitride layer.

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MohamedAmine GHEBOULI , Tayeb CHIHI, Messaoud Fatmi, Brahim GHEBOULI, Djemai .H, , (2017), Experimental and theoretical study of the structural, mechanical and electronic properties of the FeyN (y= 1, 2, 3, 4) phases, Chinese Journal of Physics, Vol:55, Issue:3, pages:674, Sciencedirect.

Using ab initio spin-polarized density functional theory calculations, the structural, elastic and thermodynamic properties of the orthorhombic and hexagonal phases of the iron carbide Fe7C3 were investigated. The calculated ground-state lattice parameters are in good agreement with the available corresponding theoretical and experimental data. The single-crystal and polycrystalline aggregate elastic constants, sound velocities, Debye temperature, brittle/ductile character and elastic anisotropy have been estimated. The calculated bulk modulus values of both considered phases are very close and are approximately equal to 262 GPa, which classifies the title compounds among the hard materials. The temperature and pressure dependencies of the unit-cell volume, bulk modulus, volume thermal expansion coefficient, isochoric and isobaric heat capacity, and Debye temperature were investigated using the quasi-harmonic Debye model.

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MohamedAmine GHEBOULI , Tayeb CHIHI, Abdelmadjid Bouhemadou, Mounir Reffas, Rabah Khenata, Brahim Ghebouli, Layachi Louail, , (2017), Structural, elastic and thermodynamic properties of iron carbide Fe7C3 phases: An ab initio study, Chinese Journal of Physics, Vol:55, Issue:3, pages:977, Sciencedirect.

We present calculations of the structural, elastic and electronic properties of nonferrous Ti, Zr, and Hf pure metals in both parent and martensitic phases in bcc and hcp structures respectively. They are based on the generalized gradient approximation (GGA) within the density functional theory. The shear modulus, Young's modulus and Poisson's ratio for Ti, Zr, and Hf metals have were calculated and compared with the corresponding experimental values. Using elastic constants obtained from calculations under the GGA, the bulk modulus along the crystallographic axes of single crystals is calculated. This is in good agreement with experiment for Ti and Zr, whereas the hcp structure for Hf is a prediction. At zero temperature and zero pressure, the bcc crystal structure is found to be mechanically unstable for Ti, Zr, and Hf. In our calculations the hcp structure is correctly found to be stable at the equilibrium volume. In the electronic density of states, the smaller n(EF) is, the more stable the compound is, in agreement with the results obtained from the total energy minimum.

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MohamedAmine GHEBOULI , Tayeb Chihi, Messaoud Fatmi, Brahim GHebouli, , (2016), Ab initio study of the parent (BCC) and martensitic (HCP) phases of nonferrous Ti, Zr, and Hf metals, Chinese Journal of Physics, Vol:54, Issue:1, pages:127, Sciencedirect.

The results of fundamental properties of zinc-blende ZnSe1−xOx ternary system and related binaries (i.e. ZnSe and ZnO) are reported using the ab initio pseudopotential-density-functional calculations. Features such as lattice constant, bulk modulus, energy gaps and electron effective mass have been determined and their variation as a function of oxygen concentration has been presented and discussed. A good agreement is obtained between the calculated results and existing experimental data. It is found that the lattice constant of the material of interest violates the Vegard's law. The information gathered from the present study could be useful for solar cells technological applications.

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MohamedAmine GHEBOULI , Abdelfatah Sami Bouarissa, Hassina Choutri, Nadir Bouarissa, , (2016), Ab initio study of electronic structure and lattice properties of ZnSe1−xOx, Optik, Vol:127, Issue:4, pages:1889, Sciencedirect.

This work presents the experimental results of the differential scanning calorimetry (DSC), hardness measurements (Hv) and X-ray diffraction (XRD) analysis, investigating the kinetics of precipitation phenomena in Al-7 wt % Mg alloy. In the XRD and DSC curves indicates the formation of the intermediate precipitation of β-(Al3Mg2) phase respectively. The activation energies associated with the processes have been determined according to the three models proposed by Kissinger, Ozawa and Boswell. Consequently, the nucleation mechanism of the precipitates can be explained. These phases are confirmed by the XRD analysis.

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MohamedAmine GHEBOULI , Messaoud Fatmi, Foudhil Sahnoun, H. Belhouchet, Tayeb CHIHI, Brahim GHEBOULI, , (2016), Thermal aging, kinetics and mechanical properties of Al-7 wt% Mg alloy, Chinese Journal of Physics, Vol:54, Issue:2, pages:216, Sciencedirect.

We report ab initio density functional theory calculations of the structural, elastic, electronic and optical properties of the double perovskite oxides Sr2AlXO6 (X=Ta, Nb, V). We have predicted a direct Г–Г band gap in Sr2AlXO6 (X=Ta, Nb) and an indirect Г–X band gap for Sr2AlVO6. The fundamental band gap increases linearly when the pressure is enhanced in the range 0–20 GPa. The frequency dependent of complex dielectric function, absorption, reflectivity and electron energy loss function were investigated in the range 0–40 eV. Features such as lattice constant, bulk modulus, elastic constants, band structure, total and local densities of states have been computed.

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MohamedAmine GHEBOULI , Brahim Ghebouli, Hassina Choutri, Messaoud Fatmi, Tayeb Chihi, Layachi Louail, Abdelmadjid Bouhemadou, Saad Bin-omran, Rabah Khenata, Hawari Khachai, , (2016), An ab initio study of the structural, elastic, electronic, optical properties and phonons of the double perovskite oxides Sr2AlXO6 (X=Ta, Nb, V), Materials Science in Semiconductor Processing, Vol:42, Issue:3, pages:405, Sciencedirect.

Structural, electronic and optical properties of inorganic aerosols, including ammonium nitrate NH4NO3 and sodium nitrate NaNO3 have been investigated using the pseudo-potential plane wave scheme in the frame of generalized gradient approximation. The geometrical parameters of the unit cell have been fully optimized and are in good agreement with the experimental data. The electronic structures show that NH4NO3 and NaNO3 have a direct gap of 3.21 eV and indirect band gap of 2.92 eV, respectively. The optical constants, including the dielectric function, refractive index, extinction coefficient, reflectivity and energy-loss spectra have been calculated and discussed. NH4NO3 and NaNO3 absorb in the ranges [75–350] and [60–380] nm respectively.

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MohamedAmine GHEBOULI , Saida Bourahla, Said Kouadri Moustefai, , (2016), Electronic and optical properties of NH4NO3 and NaNO3: an ab initio study, Indian Journal of Physics, Vol:90, Issue:8, pages:8, Springer

The PLANE WAVE pseudo-potential method within density functional theory (DFT) has been used to investigate the structural, elastic, electronic and optical properties of XCaF3 (X = K and Rb) insulating. The studied compounds show a weak resistance to shear deformation compared to the resistance to the unidirectional compression. KCaF3 and RbCaF3 are considered ductile. The elastic constants and related parameters were predicted. The stiffness is more important in KCaF3, whereas, the lateral expansion is more important in RbCaF3. KCaF3 and RbCaF3 have R- Г indirect band gap. The main peaks in the imaginary part of the dielectric function correspond to the transition from the occupied state F−p to the unoccupied states Ca: s or K, Rb: p. At lower energies, KCaF3 and RbCaF3 show the same optical properties. Under pressure effect, the peaks of imaginary part of dielectric function were shifted toward high energy.

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MohamedAmine GHEBOULI , Brahim Ghebouli, Messaoud Fatmi, Hassina Choutri, Layachi Louail, Abdelmadjid Bouhemadou, Saad Bin-omran, , (2015), Theoretical study of the structural, elastic, electronic and optical properties of XCaF3 (X = K and Rb), Solid State Sciences, Vol:43, Issue:, pages:9, Sciencedirect.

The structural, electronic and elastic properties of the M2SiC phases were studied, where M are 3d, 4d, and 5d early transition metals. The valence electron concentration (VEC) effect of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W on these properties was examined. The C44 saturates for a VEC value in surrounding of 8.5 for each serie. Hf-s, Ta-s and W-s electrons mainly contribute to the density of states at the Fermi level, and should be involved in the conduction properties. The distortion increases with increasing VEC and decreasing kc/ka factor except for the series M=Ti, V and Cr, where it is lower at the VEC value of 8.5 (it follows a parabolic variation). The M2SiC was characterized by a profound anisotropy for the shear planes (1010) and compressibility in the direction is higher than that along the cone except for W2SiC, where it is lower.

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MohamedAmine GHEBOULI , Brahim Ghebouli, Messaoud Fatmi, Layachi Louail, Tayeb Chihi, Abdelmadjid Bouhemadou, , (2015), irst-principles calculations of structural, electronic, elastic and thermal properties of phase M2SiC (M=Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W), Transactions of Nonferrous Metals Society of China, Vol:25, Issue:3, pages:915, Sciencedirect.

The quaternary iridium based hydrides NaAeIrH6 (Ae = Ca, Ba and Sr) are promising candidates as hydrogen storage materials. We have studied the structural, elastic, electronic, optical and thermodynamic properties of NaAeIrH6 (Ae = Ca, Ba and Sr) within the generalized gradient approximation, the local density approximation (LDA) and mBj in the frame of density functional perturbation theory. These alloys have a large indirect Γ–X band gap. The thermodynamic functions were computed using the phonon density of states. The origin of the possible transitions from valence band to conduction band was illustrated. By using the complex dielectric function, the optical properties such as absorption, reflectivity, loss function, refractive index and optical conductivity have been obtained.

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MohamedAmine GHEBOULI , Salim Bouras, Brahim Ghebouli, Mahfoudh Benkeri, Hassina Choutri, Layachi Louail, Tayeb Chihi, Messaoud Fatmi, Abdelmadjid Bouhemadou, Rabah Khenata, Hawari Khachai, , (2015), Theoretical characterization of quaternary iridium based hydrides NaAeIrH6 (Ae = Ca, Ba and Sr), Materials Chemistry and Physics, Vol:149, Issue:, pages:87, Sciencedirect.

Structural, elastic, electronic and mechanical properties of the M5Si3 (M = Ti, Zr) compounds with (Mn5Si3) 16H crystal structure have been studied with respect to pressure. Our computational method is based on a pseudo-potential plane-wave (PP-PW) method. The exchange correlation has been treated using the generalized gradient approximation (GGA) in order to work out the densities of states. Ground-state quantities, such as lattice parameter and bulk modulus, have been evaluated, as well as elastic constants and their pressure derivative. Elastic constants and their pressure dependence have been calculated. Also, bulk and shear moduli, Young’s modulus and Poisson’s ratio for ideal polycrystalline phases have been derived.

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MohamedAmine GHEBOULI , Tayeb CHIHI, Messaoud Fatmi, Brahim Ghebouli, Abdelmadjid Bouhemadou, , (2015), Theoretical Prediction of Structural, Elastic and Electronic Properties of M5Si3 (M = Ti, Zr) Compounds, Brazilian Journal of Physics, Vol:45, Issue:3, pages:302, Springer

Electronic band structure and lattice dynamical properties of CaxMg1−xS alloys in the rock-salt phase have been investigated. The calculations are performed in the framework of ab initio pseudo-potential approach within the generalized gradient approximation. Reasonable agreement is generally obtained between our results and the available experimental observations and previous calculations. The deviation of the alloy lattice constant and bulk modulus from linearity has been examined and discussed. Fundamental band gaps and Г–X and Г–L separations in higher-lying conduction bands are predicted. In agreement with reflectivity spectrum and recent optical absorption spectrum measurements, CaS in the rock-salt phase is found to be an indirect band-gap (Г–X). Similarly to CaS, the electronic band structure calculations showed that MgS is also an indirect band-gap (Г–X) semiconductor. However, a system transition between indirect and direct structures has been predicted in the Ca concentration range 0.12–0.83. Upon alloying the phonon modes are significantly changed showing that the longitudinal optical–transverse optical (LO–TO) splitting becomes narrower as one proceeds from pure rock-salt MgS to pure rock-salt CaS.

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MohamedAmine GHEBOULI , Hassina Choutri, Nadir Bouarissa, , (2014), Electronic structure and lattice dynamics of CaxMg1−xS in the rock-salt phase, Materials Science in Semiconductor Processing, Vol:18, Issue:, pages:71, Sciencedirect.

The structural, elastic, electronic and magnetic properties of the diluted magnetic semiconductors MnxCa1−xS in the rock-salt phase have been investigated using first-principles calculations with both LDA and LDA + U functional. Features such as lattice constant, bulk modulus, elastic constants, spin-polarized band structure, total and local densities of states have been computed. We predict the values of the exchange constants and the band edge spin splitting of the valence and conduction bands. The hybridization between S-3p and Mn-3d produces small local magnetic moment on the nonmagnetic Ca and S sites. The ferromagnetism is induced due to the exchange splitting of S-3p and Mn-3d hybridized bands. The total magnetic moment per Mn of MnxCa1−xS is 4.4μB and 4.5μB for LDA and LDA + U functional and is independent of the Mn concentration. The unfilled Mn-3d levels reduce the local magnetic moment of Mn from its free space charge value of 5μB–4.4μB and4.5μB for LDA and LDA + U functional due to 3p–3d hybridization.

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MohamedAmine GHEBOULI , Hassina Chouti, Brahim Ghebouli, Nadir Bouarissa, Ercan .Uçgun, Hamza Yasser Ocak, , (2014), Spin-polarized investigation of ferromagnetism on magnetic semiconductors MnxCa1−xS in the rock-salt phase, Materials Chemistry and Physics, Vol:148, Issue:3, pages:1000, Sciencedirect.

We employed the density-functional perturbation theory (DFPT) within the generalized gradient approximation (GGA), the local density approximation (LDA) and the virtual-crystal approximation (VCA) to study the effect of composition on the structure, stability, energy gaps, electron effective mass, the dynamic effective charge, optical and acoustical phonon frequencies and static and high dielectric constants of the rock-salt CaxMg1−xSe and CaxMg1−xTe alloys. The computed equilibrium lattice constant and bulk modulus show an important deviation from the linear concentration. From the Voigt–Reuss–Hill approximation, CaxMg1−xSe and CaxMg1−xTe present lower stiffness and lateral expansion. For Ca content ranging between 0.25 and 0.75, the elastic constants, energy gaps, electron effective mass and dynamic effective charge are predictions. The elastic constants and computed phonon dispersion curves indicate that these alloys are mechanically stable.

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MohamedAmine GHEBOULI , Hassina Choutri, Nadir Bouarissa, Brahim Ghebouli, Messaoud Fatmi, Ercan Uçgun, , (2013), Ab initio calculation of fundamental properties of CaxMg1−xA (A=Se and Te) alloys in the rock-salt structure, Physica E: Low-dimensional Systems and Nanostructures, Vol:49, Issue:, pages:83, Sciencedirect.

Results of ab initio calculations of the lattice parameter, elastic constants and some thermodynamic parameters in a wide range of pressures and temperatures are reported for the ZnSc2S4 and CdSc2S4 cubic spinels. The calculated equilibrium lattice parameters are compared with available experimental data. Elastic constants and some related properties for single-crystal and polycrystalline have been calculated at zero pressure and zero temperature using the analysis of changes in calculated stresses resulting from changes in strain. Evolution of the elastic constant with pressure and temperature is predicted. From the ab initio calculated total energy versus volume and using the quasi-harmonic Debye model, in which the phononic effects are taken into account, the evolution of some thermodynamic parameters with temperature and pressure is computed. This is the first quantitative theoretical prediction

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MohamedAmine GHEBOULI , Abd elmadjid Bouhemadou, G.Uğur, Ş.Uğur, S.Al-Essac, Rabah Khenata, Saad Bin-Omran, Yaakoub .Al-Douri, , (2013), Elastic and thermodynamic properties of ZnSc2S4 and CdSc2S4 compounds under pressure and temperature effects, Computational Materials Science, Vol:70, Issue:, pages:107, Sciencedirect.

We present results of ab initio calculations concerning lattice dynamical and thermal properties of MgS, CaS and their ternary mixed crystals CaxMg1−xS in zinc-blende structure. Results for the phonon modes, dielectric constants, Fröhlich coupling parameter, polaron effective mass, entropy and heat capacities are given for CaxMg1−xS within a composition range 0–1. Generally good agreement is obtained between our results and data available in the literature. Other case, our results are predictions.

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MohamedAmine GHEBOULI , Hassina Choutri, Nadir Bouarissa, , (2013), Lattice dynamics and thermal properties of CaxMg1−xS ternary alloys, Computational Materials Science, Vol:69, Issue:, pages:148, Sciencedirect.

Structural, electronic and optical properties of the ZnSc2S4 and CdSc2S4 cubic spinels have been investigated by means of the full-potential (linearized) augmented plane wave plus local orbitals based on density functional theory. The exchange-correlation potential is treated by the GGA–PBEsol [J.P. Perdew, A. Ruzsinszky, G.I. Csonka, O.A. Vydrov, G.E. Scuseria, L.A. Constantin, X. Zhou, K. Burke, Phys. Rev. Lett. 100 (2008) 136406] and the recently proposed modified Becke–Johnson potential approximation (mBJ) [F. Tran, P. Blaha, Phys. Rev. Lett. 102 (2009) 226401], which successfully corrects the band-gap problem found with GGA for a wide range of materials. The obtained structural parameters are in good agreement with the available experimental data. This gives support for the predict properties for ZnSc2S4 and CdSc2S4. The band structures reveal that both compounds are semiconductor with a direct gap. The obtained gap values show that mBJ is superior for estimating band gap energy. We have calculated the electron and hole effective masses in different directions. The density of states has been analyzed. Based on our electronic structure obtained using the mBJ method we have calculated various optical properties, including the complex dielectric function ɛ(ω), complex index of refraction n(ω), reflectivity coefficient R(ω), absorption coefficient α(ω) and electron energy-loss function L(ω) as functions of the photon energy. We find that the values of zero-frequency limit ɛ1(0) increase with decreasing the energy band gap in agreement with the Penn model. The origin of the peaks and structures in the optical spectra is determined in terms of the calculated energy band structures.

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MohamedAmine GHEBOULI , abdelmadjid bouhemadou, Allali Djamel, Saad Bin-omran, , (2013), Electronic and optical properties of ZnSc2S4 and CdSc2S4 cubic spinels by the modified Becke–Johnson density functional, Solid State Sciences, Vol:20, Issue:, pages:127, Sciencedirect.

We report a detailed study of the compositional dependence of the structural, elastic, electronic and dynamical properties of the quaternary alloys matched to AlP using pseudo-potential plane-wave method based on the density functional theory. The reliability and accuracy of the predicted physical properties mentioned above for are tested by comparing the calculated lattice constant, elastic constants and phonon dispersion curves for the binary AlP with the available experimental and theoretical data in the literature.

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MohamedAmine GHEBOULI , Abdelmadjid Bouhemadou, Brahim Ghebouli, Messaoud Fatmi, Saad Bin-omran, Ercan Uçgun, Hamza Yasser Ocak, , (2013), Structural, elastic, electronic and lattice dynamical properties of III-P quaternary alloys matched to AlP, Materials Science in Semiconductor Processing, Vol:16, Issue:, pages:718, Sciencedirect.

The alkaline platinum hydrides are considered the most promising as hydrogen storage materials. The alloying ability of crystal, elastic constants and related parameters, electronic and optical properties have been studied using pseudo-potential plane–wave method based on the density functional theory. The investigated compounds show a weaker resistance to compression along the principal a-axis and their resistance to shear deformation is lower than the resistance to the unidirectional compression. The band structure indicates that A2PtH6 (A=K, Rb and Cs) are X–X direct gap semiconductors. The effective electron mass at equilibrium has been predicted towards X–Γ, X–W and L–W directions. The strong hybridization between Pt-d and H-s states in the upper valence band translates the existence of covalent bonding character in these compounds. The static optical dielectric constant is inverse proportional to the fundamental gap.

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MohamedAmine GHEBOULI , Salim Bouras, Brahim Ghebouli, Mahfoudh Benkerri, Abdelmadjid Bouhemadou, , (2013), First-principles calculations on elastic, electronic and optical properties for the alkaline platinum hydrides A2PtH6 (A=K, Rb and Cs), Materials Science in Semiconductor Processing, Vol:16, Issue:3, pages:940, Sciencedirect.

The structural, elastic, electronic and optical properties of the gallium monohydrides BaGaXH (X=Si, Ge, Sn) have been investigated by means of first principles calculations. The low values of the B/G ratio of these compounds correspond to the brittle nature, which is due to the hydrogen presence. The bulk modulus, Young's modulus, shear modulus decrease from Si to Sn for BaGaXH (X=Si, Ge, Sn) in the same column in the periodic table. Also the Debye temperature of these compounds has a relative high value indicating that they possess good thermal conductivity. The mean sound velocities have a progressive decrease from silicon (Si) to tin (Sn).

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MohamedAmine GHEBOULI , Tayeb Chihi, Brahim Ghebouli, Abdelmadjid Bouhemadou, Messaoud Fatmi, Saad Bin-omran, , (2013), First-principles calculations of structural, electronic and optical properties of BaGaXH (X=Si, Ge, Sn), Materials Science in Semiconductor Processing, Vol:16, Issue:6, pages:1558, Sciencedirect.

We have applied the pseudo-potential plane wave (PP-PW) method to study the structural, elastic, and electronic properties of CuClxBr(1-x) under high pressure using the generalized gradient approximation (GGA). The effect of Cl substitutional impurities (x) on the lattice parameters for both the GGA and virtual crystal approximation (VCA) approaches were studied. The pressures at which the compounds CuClxBr(1-x) undergo a structural phase transition from ZnS type to NaCl type Pt were calculated. The elastic constants at various pressures in the 0 ＜ x ＜ 1 composition range were presented. The longitudinal-wave mode speed (VL) and transverse-wave mode speed (VT) in CuClxBr(1-x) propagating in the [100], [110], and [111] directions at zero pressure for various Cl compositions (x) in the range 0-1 were investigated. The band structure and band gap-pressure coefficients are also given. The calculated effective masses of electrons and heavy and light holes in the material under study for different concentrations x are presented.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Messaoud Fatmi, Chihi Tayeb, Ezin el abidin, Said Boucetta, , (2013), Structural, Elastic, and Electr onic Properties of CuCl x Br (1−x) Compounds under Pressure, Chinese Journal of Physics, Vol:51, Issue:, pages:738, Airiti

Based on the density functional theory as implemented in the Abinit code under the virtual crystal approximation, the lattice constant, bulk modulus, elastic constants, gap energies, electron effective mass, the dielectric constants and born effective charge in In1−x−yAlxGayAs have been calculated with both GGA and LDA in the range 0≤y≤0.9801. The optical and acoustical phonon frequencies, Fröhlich coupling parameter, deformation energy and polaron effective mass are calculated and their dependence on the Ga content is examined. For AlAs, our results are in reasonable agreement with the known data in the literature; while for other contents our treatments are predictions.

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MohamedAmine GHEBOULI , Hassina CHOUTRI, Nadir Bouarissa, Brahim GHEBOULI, , (2012), First-principles study on stability, energy gaps, optical phonon and related parameters of In1−x−yAlxGayAs alloys, Journal of Solid State Chemistry, Vol:192, Issue:0, pages:161, science direct

M3X (M=Cr, V; X=Si, Ge) compounds are studied using first-principles calculations based on the Density Functional Theory (DFT). It is found that the bulk of Cr3X (X=Si, Ge) compounds are comparable to those of Al2O3, the nearest-neighbor distance DM−M and DM−X in these compounds increase and the bulk modulus decrease, there is a strong interaction between M and M (M=Cr the interaction is stronger). Also the interaction between M (M=Cr, V) and X (X=Ge) is negative, an anti-bonding-type interaction is dominant between these atoms.

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MohamedAmine GHEBOULI , Tayeb Chihi, Messaoud Fatmi, , (2012), Ab initio study of some fundamental properties of the M3X (M=Cr, V; X=Si, Ge) compounds, Physica B: Condensed Matter, Vol:407, Issue:17, pages:3591, Sciencedirect.

Some physical properties of the cubic perovskites CsXF3 (X = Ca, Sr and Hg) have been investigated using pseudopotential plane-wave method based on the density functional theory. The calculated lattice parameters within GGA and LDA agree reasonably with the available experimental data. The elastic constants and their pressure derivatives are predicted using the static finite strain technique. We derived the bulk and shear moduli, Young's modulus, Poisson's ratio and Lamé’s constants for ideal polycrystalline aggregates. The analysis of B/G ratio indicates that CsXF3 (X = Ca, Sr and Hg) are ductile materials. The thermal effect on the volume, bulk modulus, heat capacity and Debye temperature was predicted.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Abdelmadjid Bouhemadou, Messaoud Fatmi, Rabah Khenata, Djamed Rached, Tarek Ouahrani, Saad Bin-omran, , (2012), Theoretical prediction of the structural, elastic, electronic, optical and thermal properties of the cubic perovskites CsXF3 (X = Ca, Sr and Hg) under pressure effect, Solid State Sciences, Vol:14, Issue:, pages:903, Sciencedirect.

We have carried out a first-principles density functional study of the structural, elastic and thermodynamic properties for the SnMg2O4, SnZn2O4 and SnCd2O4 cubic normal spinel structures. We have calculated the equilibrium structural parameters: the lattice constant and internal structural parameter. These results agree very well with experimental data. We have investigated the zero-pressure single-crystal and polycrystalline elastic constants and their related properties, confirming prior theoretical results for SnMg2O4 and predicting values for SnZn2O4 and SnCd2O4. The pressure dependence of the elastic constants Cij can be fit by a straight line over the range 0–30 GPa. Thermal and pressure effects on some macroscopic properties of SnMg2O4, SnZn2O4 and SnCd2O4 are predicted using the quasi-harmonic Debye model in which the lattice vibrations are taken into account

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MohamedAmine GHEBOULI , Djamel Allali, Abdelmadjid Bouhemadou, Fares Zerarga, Saad Bin-omran, , (2012), Prediction study of the elastic and thermodynamic properties of the SnMg2O4, SnZn2O4 and SnCd2O4 spinel oxides, Computational Materials Science V, Vol:60, Issue:, pages:217, Sciencedirect.

Li2PtH6 and Na2PtH6 are good candidate for hydrogen storage. The structural, elastic, electronic and optical properties of Li2PtH6 and Na2PtH6 compounds have been investigated using pseudo-potential plane–wave method based on the density functional theory. Computed lattice constant and H atom positional parameter at equilibrium agree well with the available experimental data. A quadratic pressure dependence of the elastic stiffness is found. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young's modulus, Poisson's ratio, average sound velocity and Debye temperature are numerically estimated in the framework of the Voigt–Reuss–Hill approximation for Li2PtH6 and Na2PtH6 polycrystalline aggregate. The analyses of the band structure indicates that Li2PtH6 and Na2PtH6 are indirect gap semiconductors. The static dielectric constant and static refractive index are inversely proportional to the fundamental gap.

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MohamedAmine GHEBOULI , Hassina Choutri, Nadir Bouarissa, Brahim Ghebouli, Abdelmadjid Bouhemadou, Fethi Soyalp, Ercan Uçgung, Hamza Yasser Ocak, , (2012), Theoretical prediction of the fundamental properties for the ternary Li2PtH6 and Na2PtH6, Journal of Solid State Chemistry, Vol:169, Issue:, pages:498, Sciencedirect.

Structural, elastic, electronic and magnetic properties of Mn3ZnC and Mn3GeC are investigated via ab initio calculations. Total energy calculations show that the ferromagnetic state is energetically more stable than the non-magnetic state at equilibrium volume. No found imaginary phonon frequency in the whole Brillouin zone for the two compounds supports their dynamical stability. The elastic parameters are predicted. The electrical conductivity is assured by the Mn-d electrons. The total moment comes principally from the transition metal Mn in both compounds. The magnetic moment of the Mn atom decrease considerably when the Zn atom is substituted by the Ge one.

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MohamedAmine GHEBOULI , Abdelmadjid bouhemadoui, G.Uğur, Ş.Uğur, Brahim GHebouli, Saad Bin-omran, Rabah Khenata, , (2012), Ab initio study of some fundamental physical properties of the cubic inverse-perovskite Mn3ZnC and Mn3GeC, Computational Materials Science, Vol:58, Issue:, pages:162, Sciencedirect.

Li2PtH6 and Na2PtH6 are good candidate for hydrogen storage. The structural, elastic, electronic and optical properties of Li2PtH6 and Na2PtH6 compounds have been investigated using pseudo-potential plane–wave method based on the density functional theory. Computed lattice constant and H atom positional parameter at equilibrium agree well with the available experimental data. A quadratic pressure dependence of the elastic stiffness is found. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young's modulus, Poisson's ratio, average sound velocity and Debye temperature are numerically estimated in the framework of the Voigt–Reuss–Hill approximation for Li2PtH6 and Na2PtH6 polycrystalline aggregate. The analyses of the band structure indicates that Li2PtH6 and Na2PtH6 are indirect gap semiconductors. The static dielectric constant and static refractive index are inversely proportional to the fundamental gap.

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MohamedAmine GHEBOULI , ,(2012), Theoretical prediction of the fundamental properties for the ternary Li2PtH6 and Na2PtH6,First international conference On innovatives materials and techniques,Tunisie

The structural, elastic, electronic, optical and thermal properties of the semiconductor perovskite CsPbCl3 were investigated using the pseudo-potential plane wave (PP-PW) scheme in the frame of generalized gradient approximation (GGA) and local density approximation (LDA). The computed lattice constant agrees reasonably with experimental and theoretical ones. The CsPbCl3 crystal behaves as ductile material. The valence bands are separated from the conduction bands by a direct band gap R–R. We distinguished hybridization between Pb-p states and Cl-p states in the valence bonding region. Under compression at P=30 GPa, this material will have a metallic character. The thermal effect on the lattice constant, bulk modulus, Debye temperature and heat capacity CV was predicted using the quasi-harmonic Debye model. To the author's knowledge, most of the studied properties are reported for the first time.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Messaoud Fatmi, , (2011), First-principles calculations on structural, elastic, electronic, optical and thermal properties of CsPbCl3 perovskite, Physica B: Condensed Matter, Vol:406, Issue:9, pages:1837, science direct

A theoretical study on the structural, elastic, electronic and lattice dynamic properties of AlxYyB1−x−yN quaternary alloys in zinc-blend phase has been carried out with first-principles methods. Information on the lattice parameter, the lattice matching to available substrates and energy band-gaps is a prerequisite for many practical applications. The dependence of the lattice parameter a, bulk modulus B, elastic constants C11, C12 and C44, band-gaps, optical phonon frequencies (ωTO and ωLO), the static and high-frequency dielectric coefficients ε (0) and ε (∞) and the dynamic effective charge Z⁎ were analyzed for y=0, 0.121, 0.241, 0.362 and 0.483. A significant deviation of the bulk modulus from linear concentration dependence was observed. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young's modulus, Poisson's ratio are numerically estimated in the frame work of the Voigt–Reuss–Hill approximation. The resistance to changes in bond length and lateral expansion in AlxYyB1−x−yN increase with increasing y concentration. We observe that at y concentration about 0.035 and 0.063, AlxYyB1−x−yN changes from brittle to ductile and Γ–X indirect fundamental gap becomes Γ–Γ direct fundamental gap. There is good agreement between our results and the available experimental data for the binary compound AlN, which is a support for those of the quaternary alloys that we report for the first time.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Messaoud FATMI, , (2011), Theoretical studies of structural, elastic, electronic and lattice dynamic properties of AlxYyB1−x−yN quaternary alloys, Physica B: Condensed Matter, Vol:406, Issue:13, pages:2521, science direct

The structural, elastic, electronic and thermal properties of the MAX phases Ti2SiC and Cr2SiC are studied by means of the pseudo-potential plane wave method within GGA and LDA. The effect of pressure on the normalized lattice constants a/a0 and c/c0 and the internal parameter z is investigated. Our results of elastic constants, sound velocities and Debye temperature are predictions. The Ti2SiC and Cr2SiC compounds behave as ductile material and show a stronger anisotropy. The analysis of the band structure and density of states show that these compounds are electrical conductors, having a strong directional bonding between Ti and C and Cr and C atoms assured by the hybridization of Ti–d and Cr–d atom states with C–p atom states. The thermal effect on the primitive cell volume, bulk modulus, heat capacities CV and CP were predicted using the quasi-harmonic Debye model.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Messaoud FATMI, Abdelmadjid Bouhemadou, , (2011), Theoretical prediction of the structural, elastic, electronic and thermal properties of the MAX phases X2SiC (X = Ti and Cr), Intermetallics, Vol:19, Issue:12, pages:1936, science direct

Density functional theory pseudo-potential plane-wave calculations are performed in order to predict the structural, elastic and thermodynamic properties of the newly discovered tetragonal intermetallic SrPd2Ge2. The computed equilibrium lattice constants and the internal parameter are in good agreement with the experimental findings. The effect of high pressure, up to 40 GPa, on the lattice constants shows that the contraction along the axis is higher than along the axis. The single-crystal elastic constants and related properties are calculated using the static finite strain technique. We predicted the bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio for ideal polycrystalline SrPd2Ge2 aggregates, using the Voigt–Reuss–Hill approximations. We estimated the Debye temperature and minimum thermal conductivity of SrPd2Ge2 from the average sound velocity. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the temperature and pressure effects on the primitive cell volume, bulk modulus, thermal expansion coefficient, heat capacity and Debye temperature are investigated. This is the first quantitative theoretical prediction of the elastic and thermodynamic properties of the SrPd2Ge2 compound, and it still awaits experimental confirmation.

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MohamedAmine GHEBOULI , Abdelmadjid Bouhemadou, Brahim Ghebouli, Messaoud Fatmi, Saad Bin-omran, , (2011), Prediction study of the elastic and thermodynamic properties of the newly discovered tetragonal SrPd2Ge2 phase, Solid State Communications, Vol:151, Issue:14, pages:976, science direct

A computed investigation on the structural, elastic, electronic, phonon frequencies and thermal properties of AlxScyB1−x−yN quaternary alloys in the zinc-blend phase has been made with first-principles methods. The information on the lattice constant, lattice matching to AlN substrate and energy band gaps is indispensable for various practical applications. We have studied the effect of Sc concentration y (y = 0, 0.152, 0.303, 0.455 and 0.607) on the lattice constant, bulk modulus, elastic constants C11, C12 and C44, band gaps, optical phonon frequencies (ωTO and ωLO), static and high-frequency dielectric coefficient ɛ(0) and ɛ(∞) and dynamic effective charge Z*. We remark an important deviation from the linear concentration dependence of the lattice constant and bulk modulus. The shear moduli, Young's modulus, Poisson's ratio were estimated in the frame work of the Voigt–Reuss–Hill approximation. The resistance to changes in bond length and lateral expansion in AlxScyB1−x−yN increase with increasing y concentration. We observe that at y concentration about 0.11, the Г–X indirect fundamental gap becomes Г–Γ direct fundamental gap in AlxScyB1−x−yN. There is well agreement between our results and the experiment data for AlN binary compound which is a support for those of the quaternary alloys that we report for the first time.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Messaoud Fatmi, Lebgaa Noudjoud, , (2011), Theoretical investigations of physical properties of AlxScyB1−x−yN quaternary alloys, Materials Chemistry and Physics, Vol:128, Issue:1, pages:195, science direct

Various physical properties of the cubic perovskite-type oxide BiScO3 have been investigated using the pseudo-potential plane-wave (PP-PW) method based on the density functional theory (DFT). The computed equilibrium lattice parameters agree well with the available theoretical data. The elastic constants and their pressure dependence are predicted using the static finite strain technique. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature are numerically estimated in the framework of the Voigt–Reuss–Hill approximation for BiScO3 polycrystalline aggregate. The analysis of the site-projected -decomposed density of states, charge transfer and charge density shows that bonding is predominantly of ionic nature. We distinguish hybridization between Sc-d states and - states in the valence bonding region. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the thermal effect on the lattice constant, bulk modulus, heat capacities and thermal expansion coefficient is calculated.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Messaoud Fatmi, Bouhemadou Abdelmadjid, , (2011), Calculation of physical properties of the cubic perovskite-type oxide BiScO3 using the PP-PW method based on the DFT theory, Solid State Communications, Vol:151, Issue:12, pages:908, science direct

The structural, electronic, optical and thermodynamic properties of SrxCa1−xO, BaxSr1−xO and BaxCa1−xO ternary alloys in NaCl phase were studied using pseudo-potential plane-wave method within the density functional theory. We modeled the alloys at some selected compositions with ordered structures described in terms of periodically repeated supercells. The dependence of the lattice parameters, band gaps, dielectric constants, refractive indices, Debye temperatures, mixing entropies and heat capacities on the composition x were analyzed for x = 0, 0.25, 0.50, 0.75 and 1. The lattice constant for SrxCa1−xO and BaxSr1−xO exhibits a marginal deviation from the Vegard's law, while the BaxCa1−xO lattice constant exhibits an appreciable upward bowing. A strong deviation of the bulk modulus from linear concentration dependence was observed for the three alloys. The microscopic origins of the gap bowing were detailed and explained. The composition dependence of the dielectric constant and refractive index was studied using different models. The thermodynamic stability of these alloys was investigated by calculating the phase diagram. The thermal effect on some macroscopic properties was investigated using the quasi-harmonic Debye model. There is a good agreement between our results and the available experimental data for the binary compounds which may be a support for the results of the ternary alloys reported here for the first time.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Abdelmadjid Bouhemadou, Messaoud Fatmi, Khaled Bouamama, , (2011), Structural, electronic, optical and thermodynamic properties of SrxCa1−xO, BaxSr1−xO and BaxCa1−xO alloys, Journal of Alloys and Compounds, Vol:509, Issue:5, pages:1440, science direct

The structural, elastic, electronic, optical and thermal properties of α phase in LiBeN semiconductor have been studied using pseudo-potential plane wave method based on the density functional theory. The computed lattice parameter agrees well with previous theoretical work. The elastic constants and their pressure dependence are predicted using the static finite strain technique. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature are numerically estimated in the frame work of the Voigt–Reuss–Hill approximation for α-LiBeN polycrystalline aggregate. The assignments of the structures in the optical spectra and band structure transitions have been examined and discussed. The thermal effect on heat capacities is investigated by the quasi-harmonic Debye model. To the best of our knowledge, most of the studied properties of the material of interest are reported for the first time.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Nadir bouarissa, Messaoud FATMI, , (2011), Band parameters of α-LiBeN semiconductor from density functional calculations, Superlattices and Microstructures, Vol:50, Issue:4, pages:319, science direct

The isothermal and non-isothermal ageing of an Al-2.4 wt% Cu alloy have been studied using X-ray diffraction analysis and differential scanning calorimetry (DSC) at different heating rates. Quantitative metallography methods have been applied to measure the corresponding transformed volume fractions at various temperatures and times of precipitation. The variation of the heating rate using DSC technique has allowed us to calculate two kinetics parameters of precipitation which are the Avrami exponent and the activation energy of the process using Kissinger, Ozawa and Bosswell methods. These parameters are similar to those found for the precipitation reaction of θ′ and θ (Al2Cu) phases.

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MohamedAmine GHEBOULI , Messaoud fatmi, Brahim ghebouli, tayeb CHIHI, M. Abdulhafid, , (2011), The kinetics of precipitation in Al-2.4 wt% Cu alloy by Kissinger, Ozawa, Bosswel and Matusita methods, Physica B: Condensed Matter, Vol:406, Issue:11, pages:2277, science direct

Structural, elastic, electronic and thermal properties of the MAX phase Nb2SiC are studied by means of a pseudo-potential plane-wave method based on the density functional theory. The optimized zero pressure geometrical parameters are in good agreement with the available theoretical data. The effect of high pressure, up to 40 GPa, on the lattice constants shows that the contractions along the -axis were higher than those along the -axis. The elastic constants and elastic wave velocities are calculated for monocrystal Nb2SiC. Numerical estimations of the bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature for ideal polycrystalline Nb2SiC aggregates are performed in the framework of the Voigt–Reuss–Hill approximation. The band structure shows that Nb2SiC is an electrical conductor. The analysis of the atomic site projected densities and the charge density distribution shows that the bonding is of covalent–ionic nature with the presence of metallic character. The density of states at Fermi level is dictated by the niobium d states; Si element has a little effect. Thermal effects on some macroscopic properties of Nb2SiC are predicted using the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variations of the primitive cell volume, volume expansion coefficient, bulk modulus, heat capacity and Debye temperature with pressure and temperature in the ranges of 0–40 GPa and 0–2000 K are obtained successfully.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Abdelmadjid Bouhemadou, Messaoud FATMI, , (2011), Theoretical study of the structural, elastic, electronic and thermal properties of the MAX phase Nb2SiC, Solid State Communications, Vol:151, Issue:5, pages:382, science direct

The structural, elastic, electronic, optical and thermodynamic properties of the cubic perovskite-type hydride KMgH3 have been investigated using pseudo-potential plane-wave method based on the density functional theory. Computed equilibrium lattice constant agrees well with the available experimental and theoretical data. The elastic constants and their pressure dependence are predicted using the static finite strain technique. A linear pressure dependence of the elastic stiffnesses is found. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young’s modulus, Poisson’s ratio, average sound velocity and Debye temperature are numerically estimated in the frame work of the Voigt–Reuss–Hill approximation for KMgH3 polycrystalline aggregate. The analysis of the site-projected l-decomposed density of states and charge density shows that the bonding is predominantly of ionic nature. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the temperature effect on the lattice constant, bulk modulus, heat capacity and Debye temperature is calculated.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Bouhemadou Abdelmadjid, Messaoud FATMI, Saad Bin-omran, , (2011), Structural, elastic, electronic, optical and thermodynamic properties of KMgH3, Solid State Sciences, Vol:13, Issue:3, pages:647, science direct

The relation between the continuous and discontinuous precipitations, and the discontinous precipitation kinetics and mechanisms in Cu-13 wt.% Sn and Al-20 wt.% Ag alloys, have been investigated by metallographic observations, differential scanning calorimetry, X-ray diffraction and microhardness measurements. During ageing of the supersaturated solid solution of Al-Ag, after the preprecipitation of the Guinier Preston zones and the continuous precipitation of the plates of the transition phase γ′, the cellular precipitation of the equilibrium phase γ occurs and grows from the grain boundaries but lamellae are not perpendicular to the reaction front. At high temperature intergranular precipitation occurs without the reaction front or cell. Both types of precipitation occur in the Cu-13 wt.% Sn alloy but very slowly. However, continuous precipitation predominates after a high deformation amount and reduces the amount of chemical driving available for both the initiation and propagation of discontinuous precipitation.

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MohamedAmine GHEBOULI , ,(2011), Precipitation phenomena study during Ageing of Cu Sn and Al-Ag Alloys,International Science and Technology Conference (ISTEC), 7- 9 December 2011,Istanbul

We have applied the pseudo-potential plane wave method to study the structural, elastic, electronic, lattice dynamic and optical properties of GaN and AlN in the wurtzite lattice and BN with zinc-blende structure. We have found that all elastic constants depend strongly on hydrostatic pressure, except for C44 in wurtzite AlN and GaN that shows a weaker dependence. AlN and GaN present a direct band gap 0–0, whereas BN has an indirect band gap 0–X. The indirect 0–K band gap in AlN occurs at about 35 GPa. The top of the valence bands reflects the p electronic character for all structures. There is a gap between optical and acoustic modes only for wurtzite phases AlN and GaN. All peaks in the imaginary part of the dielectric function for the wurtzite lattice GaN and AlN move towards lower energies, while those in the zinc-blende BN structure shift towards higher energies with increasing pressure. The decrease of the static dielectric constant and static refractive index in zinc-blende BN is weaker and it can be explained by its higher elastic constants.

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MohamedAmine GHEBOULI , Messaoud FATMI, Brahim GHEBOULI, Zein el abidin heiba, , (2011), First-principles study of structural, elastic, electronic, lattice dynamic and optical properties of XN (X = Ga, Al and B) compounds under pressure, Physica Scripta, Vol:83, Issue:83, pages:65702, Springer

We have investigated the structural, elastic, electronic, optical and thermal properties of aninsulator perovskite CsCdF3using the pseudo-potential plane wave (PP-PW) scheme in the frame ofgeneralized gradient approximation (GGA) and local density approximation (LDA). The computed latticeparameter and bulk modulus agree reasonably with experimental and previous theoretical works. We findthat the cubic Pm-3m crystal symmetry persists throughout the pressure range studied. The anisotropyin CsCdF3crystal is strong, while, by analyzing the ratio between the bulk and shear moduli, we concludethat CsCdF3is ductile material. The calculations reveal that CsCdF3is an indirect-gap insulator underambient conditions, with the gap increasing under pressure. Also, we present the results of the densities ofstates and charge densities. The static dielectric constant and static refractive index are proportional tothe fundamental indirect band gap Γ-R. The thermal effect on the volume, bulk modulus, heat capacitiesCVandCPand Debye temperature was predicted using the quasi-harmonic Debye model. To the author’sknowledge, most of the studied properties are reported for the first time

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Messaoud FATMI, , (2011), Structural, elastic, electronic, optical and thermal propertiesof cubic perovskite CsCdF3under pressure effec, THEEUROPEANPHYSICALJOURNALAPPLIEDPHYSICS, Vol:53, Issue:, pages:30101, Springer

The structural, elastic, electronic and optical properties of XO (X= Ca, Sr and Ba) compounds were investigated by the density functional theory. A good agreement was found between our calculated results and the available theoretical and experimental data of the lattice constants. Young's modulus, Poisson ratio, bulk modulus, elastic constants and their pressure derivatives are also calculated. SrO and BaO compounds present a transition phase at 39.72 and 27.28 GPa. The SrO compound shows a change from direct band gap (Γ–Γ) to indirect band gap (Γ–X) at about 15 GPa. The top of the valence bands reflects the s electronic character for all structures. We investigate the effective mass of electrons as function of pressure at the Γ point for CaO, SrO and BaO compounds. Calculations of the optical spectra have been performed for the energy range 0–60 eV. The origin of the spectral peaks was interpreted based on the electronic structures. The enhancement of pressure increases the static dielectric function and refractive index of CaO, SrO and BaO.

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MohamedAmine GHEBOULI , Brahim Ghebouli, Messaoud Fatmi, Mahfoud Benkarri, , (2010), First-principles calculations of structural, elastic, electronic and optical properties of XO (X=Ca, Sr and Ba) compounds under pressure effect, Materials Science in Semiconductor Processing, Vol:13, Issue:2, pages:92, science direct

Information on the energy band gaps, the lattice parameters and the lattice matching to available substrates is a prerequisite for many practical applications. A pseudopotential plane-wave method as implemented in the ABINIT code is used to the AsxPyN1−x−yAl quaternary alloys lattice matched to AlP substrate to predict their energy band gaps and optical properties. The range of compositions for which the alloy is lattice-matched to AlP is determined. Very good agreement is obtained between the calculated values and the available experimental data. The Debye temperature increase when the bulk modulus is enhanced. We study the variation of elastic constants, the optical phonon frequencies (ωTO and ωLO), the static and high-frequency dielectric coefficient ɛ(0) and ɛ(∞) and the dynamic effective charge Z* with P concentration (y).

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MohamedAmine GHEBOULI , Brahim Ghebouli, Messaoud Fatmi, Tayeb Chihi, Said Boucetta, , (2010), First-principles study of structural, elastic, electronic and lattice dynamic properties of AsxPyN1−x−yAl quaternary alloys, Journal of Alloys and Compounds, Vol:507, Issue:1, pages:120, science direct

The structural, elastic, electronic, optical and thermodynamic properties of the perovskite chloride CsCdCl3 were investigated using the pseudo-potential plane wave (PP-PW) within the Generalized Gradient Approximation (GGA) and Local Density Approximation (LDA). The computed lattice parameter agrees well with experimental and previous theoretical works. Based on the elastic constants and their related parameters, the crystal rigidity and mechanical stability have been discussed. Energy band structure shows that the investigated material is indirect energy band gap semiconductor. The static dielectric constant and static refractive index are indeed, proportional to the fundamental indirect band gap. The thermal effect on the lattice parameter, bulk modulus, volume expansion coefficient, Grüneisen parameter, heat capacities and Debye temperature were predicted using the quasi-harmonic Debye model. To the best of the authors’ knowledge, most of the studied properties are reported for the first time.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Messaoud Fatmi, Abdelmadjid Bouhemadou, , (2010), First-principles study of the structural, elastic, electronic, optical and thermodynamic properties of the cubic perovskite CsCdCl3 under high pressure, Solid State Communications, Vol:150, Issue:39, pages:1896, science direct

The stability, structural parameters, elastic constants, electronic and optical properties of perovskites CsCaH3 and RbCaH3 were investigated by the density functional theory. The calculated lattice parameters are in agreement with previous calculation and experimental data. The energy band structures, density of states, born-effective-charge and Mulliken charge population were obtained. The perovskites CsCaH3 and RbCaH3 present a direct band gap of 3.15 eV and 3.27 eV at equilibrium. The top of the valence bands reflects the s electronic character for both structures. Furthermore, the absorption spectrum, refractive index, extinction coefficient, reflectivity, energy-loss spectrum, and dielectric function were calculated. The origin of the spectral peaks was interpreted based on the electronic structures. The static dielectric constant and refractive index are indeed, inverse proportional to the direct band gap.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Messaoud Fatmi, , (2010), First-principles study of structural, elastic, electronic and optical properties of perovskites XCaH3 (X = Cs and Rb) under pressure, Solid State Sciences, Vol:12, Issue:4, pages:587, science direct

Information on the energy band gaps, the lattice parameters and the lattice matching to available substrates is a prerequisite for many practical applications. A pseudopotential plane-wave method as implemented in the ABINIT code is used to the AsxPyN1−x−yB quaternary alloys lattice matched to BP substrate to predict their energy band gaps and lattice dynamic properties. The range of compositions for which the alloy is lattice matched to BP is determined. Very good agreement is obtained between the calculated values and the available experimental data. The compositional dependence of direct and indirect band gaps has been investigated. We study the variation of elastic constants, the optical phonon frequencies (ωTO and ωLO), the high-frequency dielectric coefficient ε(∞) and the born effective charge Z∗ with P concentration.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Messaoud Fatmi, Said Ibrahim Ahmed, , (2010), First-principles study of structural, elastic, electronic and lattice dynamic properties of AsxPyN1−x−yB quaternary alloys, Computational Materials Science, Vol:48, Issue:1, pages:94, science direct

We present structural, elastic, electronic and optical properties of the perovskites SrMO3 (M=Ti, and Sn) for different pressure. The computational method is based on the pseudo-potential plane wave method (PP-PW). The exchange-correlation energy is described in the generalized gradient approximation (GGA). The calculated equilibrium lattice parameters are in reasonable agreement with the available experimental data. This work shows that the perovskites SrTiO3, and SrSnO3 are mechanically stable and present an indirect band gaps at the Fermi level. Applied pressure does not change the shape of the total valence electronic charge density and most of the electronic charge density is shifted toward O atom. Furthermore, in order to understand the optical properties of SrMO3, the dielectric function, absorption coefficient, optical reflectivity, refractive index, extinction coefficient and electron energy-loss are calculated for radiation up to 80 eV. The enhancement of pressure decreases the dielectric function and refractive indices of SrTiO3 and SrSnO3.

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MohamedAmine GHEBOULI , Brahim GHEBOULI, Tayeb Chihi, Messaoud Fatmi, Said Boucetta, Mounir Reffas, , (2009), First-principles study of structural, elastic, electronic and optical properties of SrMO3 (M=Ti and Sn), Solid State Communications, Vol:149, Issue:47, pages:2244, science direct