DJAMEL Allali

شوية رابح

دراسة واستخدام مواد نانوية من أكسيد النحاس للتحويل الكهروضوئي

غويني إلهام

مساهمة في دراسة الخواص البنيوية والإلكترونية والضوئية والمرونة للمواد البيروفسكية

طرافي نور الهدى

مساهمة في دراسة الخواص الفيزيائية لبعض المواد السبينالية الأوكسيدية

رفافسة أسماء

دراسة بعض المركبات المغناطيسية السبينالية الأوكسيدية

بلحوت سعيدة

تاثيرإضافة CaOعلى تحضير و دراسة السبينال MgAl2O4 المحضر إنطلاقا من مساحيق نانومترية

موسى حيزية

Structural, electronic and optical properties of Ag-based oxides XAgO (X= Li and Na): An ab initio study

نشنش الطيب

تحضير و دراسة آلية تشكل المركب MgAl2O4 إنطلاقا من مساحيق نانومترية

ZANAT Soulaf

Contribution à l’étude des propriétés structurales et thermodynamiques des composés LiZnP, LiZnAs et LiZnSb

HARHOUZ Fatma

Etude ab-initio des propriétés électroniques et optiques des spinelles GeMg2O4, GeZn2O4 et GeCd2O4

This study aims to prepare manganese-doped zinc oxide (MZO) thin films with low Mn content (x = 0, 2, 4 %) using the sol–gel spin coating method and to characterize their structural, optical, and magnetic properties. Experimental techniques were complemented by Density Functional Theory calculations with Hubbard correction (DFT-LDA + U). All films exhibit a polycrystalline wurtzite hexagonal phase of ZnO. As the Mn doping increases, all diffraction peaks are getting weaker, which leads to deterioration in the crystallinity of the samples. Furthermore, Mn doping affects the grain size (57.44–38.20 nm), the surface morphology (rms: 45.24–30.47 nm), the transmittance (93–54 %) and the optical band gap energy (Eg: 3.27–3.18 eV). Photoluminescence spectra reveals ultraviolet peaks (386–395 nm) along with weak green (525 nm) and strong (438 nm) and weak (475 nm) blue peaks. DFT-LDA + U calculations exhibits an antiferromagnetic phase with slightly reduced Eg (3.379 eV for x = 0 % and 3.267 for 3.7 %), attributed to the influence of Mn3d states near the Fermi level. This study presents a comprehensive analysis of low-content Mn-doped ZnO thin films by combining experimental and theoretical approaches. The findings provide valuable insights into the electronic, structural, optical, and magnetic properties of MZO, emphasizing the critical role of Mn 3d states in altering the magnetic behavior and adjusting Eg.

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ELHADJ Benrezgua , Rabie AMARI , AMMAR Boukhari , Djamel ALLALI , Smail TERCHI , Bahri DEGHFEL , ABDELHAMID Guelil , Abdelhalim Zoukel, Ahmad Azmin Mohamad, , (2025-02-01), Synthesis of low-content Mn-doped ZnO thin films: Characterizations and density functional theory studies, Inorganic Chemistry Communications, Vol:172, Issue:172, pages:113710, Elsevier, Science Direct

Using the full-potential linearised augmented plane wave approach, we examined the structural, electronic, and optical features of AgXBr3 perovskite materials (X = Ca, Sr, or Ba). The GGA-PBEsol exchange-correlation functional yields equilibrium structure parameters that match the literature. Electronic structure analysis demonstrates that the Tran– Blaha modified Becke–Johnson and screened hybrid HSE06 functionals widen the bandgap compared to GGA-PBEsol. As X’s atomic size rises, its indirect fundamental bandgap lowers. The density of states diagrams, complex dielectric function, electronic energy loss function, absorption coefficient, reflectivity, extinction coefficient, and refractive index were thoroughly explored. Results show that reducing the bandgap increases the dielectric function’s zero frequency limits. Origins of optical spectra peaks and characteristics have been identified.

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Djamel ALLALI , Abdelhak Bedjaoui, Abdelmadjid Bouhemadou, , (2025-01-07), Investigation of the structural, electronic and optical properties of halide perovskites AgXBr3 (X = Ca, Sr, and Ba) using DFT framework, Indian Journal of Physics, Vol:99, Issue:99, pages:1-13, Springer

This study provides crucial information on the fundamental physical characteristics of Ba2NbBO6 (B = As, Sb, and Bi) double perovskites with rhombohedral structure. These compounds are thermodynamically stable in their rhombohedral shape over a pressure range of −20–30 GPa. Electronic structure calculations revealed that Ba2NbAsO6, Ba2NbSbO6, and Na2NbBiO6 are semiconductors with energy bandgaps of 2.101 eV, 1.71 eV, and 2.813 eV, respectively. By analyzing the calculation results from the quantum theory of atoms in molecules, it is expected that the Nb-O and As/Sb/Bi-O bonds to have covalent features. In contract, Basingle bondO and Basingle bondAs/Sb/Bi bonds exhibit ionic characteristics. We also determined the real and imaginary parts of the dielectric function, absorption coefficient, optical conductivity, loss energy function, reflectivity, refractive index, and extinction coefficient as function of the incident light energy.

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SABER Saad Essaoud , MOHAMMED ELAMIN KETFI , Djamel ALLALI , Missoum Radjai, Abdelmadjid Bouhemadou, , (2024-12-14), Fundamental physical features of the rhombohedral structure of double perovskite compounds Ba2NbBO6 (B = As, Sb, and Bi), Chemical Physics, Vol:591, Issue:1, pages:112578, Elsivier

Ce cours de physique I (Polycopié rappels des cours et exercices résolus: Mécanique du point matériel) a été rédigé à l’intention des étudiants qui préparent, une licence dans les domaines des Sciences de la Matière et des Sciences et Technologies. Il est conforme au programme officiel. Le premier chapitre est consacré à des rappels sur l’algèbre vectorielle et l’analyse dimensionnelle. Les deux traitent des grandeurs physiques de base qui sont utilisées pour l’expression des lois physiques. En plus des rappels nécessaires, l’objectif de cette partie est d’introduire des définitions claires et des notations appropriées. Le deuxième chapitre est dédié à la cinématique. Son but est de décrire les mouvements d’objets sans s’intéresser aux causes qui les produisent. Il traite uniquement des mouvements de points matériels c’est-à-dire exclusivement des translations. Le troisième chapitre traite de la dynamique du point matériel, dans le cadre de la mécanique de Newton avec ses trois lois ou principes indissociables: la loi d’inertie, la loi fondamentale de la dynamique et la loi des actions réciproques. Nous y considérons les lois générales, dites lois de forces, établies pour un certain nombre d’interactions avec des applications destinées à la prévision des mouvements des corps. La notion de moment cinétique d’une particule par rapport à l’origine et celle des pseudo-forces y sont également traitées. Le quatrième chapitre concerne la troisième méthode d’analyse qui est celle du travail et de l’énergie. Cette approche élimine le calcul de l’accélération en reliant directement la force, la masse, la vitesse et le déplacement. Nous considérons d’abord le travail d’une force et l’énergie cinétique d’une particule. Nous traitons ensuite les notions d’énergies potentielle et totale que nous appliquons au principe de conservation de l’énergie dans diverses situations pratiques.

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DjamelALLALI , ,(2024-11-15); Cours de Physique I Polycopié rappels des cours, exercices et examens résolus : Mécanique du point matériel,جامعة محمد بوضياف المسيلة,

We investigated the effects of externally applied pressure on the Sr2P7Br compound’s properties, specifically its crystalline structure, elasticity, and thermodynamics. This investigation was carried out using the pseudopotential plane wave method within the framework of density functional theory. We used the well-known PBEsol variant of the exchange–correlation general gradient approximation specifically designed for solid-state analysis. This is the first endeavor to investigate the effects of pressure on the Sr2P7Br material using a theoretical approach. The computed equilibrium structural parameters closely match the relevant experimental counterpart values. The determined elastic constants, obtained under both ambient pressure and hydrostatic pressures up to 18 GPa, satisfy the mechanical stability requirements. Based on the computed Pugh’s ratio, Cauchy pressure, and Poisson’s ratio, it can be concluded that the Sr2P7Br compound exhibits ductile behavior. The polycrystalline elastic moduli, including the isotropic bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio, at ambient pressure and under pressure effects, were derived from the single-crystal elastic constants. Additionally, associated parameters, such as average sound velocity, Debye temperature, minimum thermal conductivity, and Vickers hardness, were examined under pressure influences. The quasi-harmonic Debye approximation was used to investigate the relationship between temperature and some macroscopic physical parameters, such as lattice parameter, bulk modulus, Debye temperature, volume thermal expansion coefficient, and isobaric and isochoric heat capacities, at fixed pressures of 0, 4, 8, 12, and 16 GPa. The results derived from the elastic constants exhibit substantial concordance with those computed using the Debye quasi-harmonic model, thereby validating the reliability of our findings.

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SABER Saad Essaoud , Djamel ALLALI , ADMIN Admin , ADMIN Admin , Abdelmadjid Bouhemadou, Missoum Radjai, Abdelhak Bedjaoui, , (2024-11-10), The Structural, Elastic, and thermodynamic properties of Sr2P7Br Double Zintl salt with heptaphosphanortricyclane configuration, Computational and Theoretical Chemistry, Vol:1242, Issue:, pages:114947-114958, Elsevier

We present and analyze the findings of a comprehensive ab initio computation that examines the electronic, optical, and thermoelectric characteristics of a recently synthesized Zintl compound known as CsGaSb2. The electronic and optical characteristics were examined using the DFT-based FP-L/APW+loapproach. Toaddress the exchange–correlation effects, we employed the GGA-PBEsol and TB-mBJ approaches.The CsGaSb2 semiconductor exhibits an indirect bandgap of 0.695 eV when analyzed with the GGA-PBEsol approach, and a bandgap of 1.254 eV when analyzed with the TB-mBJ approach.The PDOS diagrams were used to discover the origins of the electronic states that make up the energy bands. The charge density study reveals that the Ga-Sb link within the [GaSb2] block is mostly governed by a covalent character, whereas the cation Cs+ and polyanion [MSb2]−bonding is predominantly ionic. The frequency dependence of macroscopic linear optical coefficients was evaluated over a broad range of photon energies from 0 to 25 eV. The thermoelectric characteristics were investigated via the Boltzmann kinetic transport theoryassuming a constant relaxation time.The compound's figure of merit at a temperature of 900 K is roughly 0.8.

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SABER Saad Essaoud , MOHAMMED ELAMIN KETFI , Djamel ALLALI , Sumayah Al-Essa, Saad Bin-Omran, Missoum Radjai, Said Maabed, Rabah Khenata, Abdelmadjid Bouhemadou, Sumayah Al-Essa, Fatima Djilani, , (2024-08-27), An ab initio analysis of the electronic, optical, and thermoelectric characteristics of the Zintl phase CsGaSb2, Physica Scripta, Vol:99, Issue:9, pages:095996-096009, IOPscience

The structural, electronic, and optical characteristics of the perovskites BaXCl3 (X = Li, Na) were thoroughly explored utilizing the full potential linear augmented plane wave approach within the density functional theory framework. When calculating structural properties, the exchange–correlation interactions were studied using the GGA-PBEsol functional, whereas when computing electronic and optical properties, they were analyzed using the TB-mBJ functional. The Equilibrium lattice parameters and bulk modulus were calculated by fitting total energy as a function of volume to the Birch-Murnaghan equation of state. Energy band dispersions estimated using the TB-mBJ method reveal that BaLiCl3 has an indirect R-Γ-type bandgap of 5.57 eV, while BaNaCl3 exhibits a direct Γ-Γ-type bandgap of 5.59 eV. Densities of state diagrams were used to further understand the characteristics of the energy bands. The Frequency dependency of the dielectric function, absorption coefficient, refractive index, optical reflectivity, and energy loss function was investigated over the energy range of 0 to 30 eV. The computed optical spectra indicate that these perovskites have substantial promise for UV-related applications.

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SABER Saad Essaoud , Djamel ALLALI , ADMIN Admin , ADMIN Admin , Sarah Chaba Mouna, Djamel Houatis, Missoum Radjai, Md. Atikur Rahman, Abdelmadjid Bouhemadou, Hatem Allaf, Hüsnü Kara, , (2024-07-16), Structural, electronic, and optical characteristics of BaXCl3 (X = Li, Na) perovskites, Materials Science and Engineering: B, Vol:308, Issue:, pages:117578-117588, Elsevier

We present the results of a comprehensive investigation using the full-potential linearized augmented plane wave approach to analyze the structural characteristics, electronic structures, and optical spectra of the perovskite compounds CaLiX3 (X = Cl, Br, or I). Various functionals were employed to simulate the exchange–correlation interactions. The calculated equilibrium structural parameters, obtained using the generalized gradient approximation, are consistent with the existing findings in the literature. The computed electronic structures reveal that the Tran–Blaha modified Becke–Johnson potential significantly enhances the bandgap. For all CaLiX3 compounds studied, we predicted an indirect bandgap. Additionally, we observed a gradual decrease in the bandgap as the atomic size of the X element increases. The electronic states constituting the various energy bands were evaluated by computing the partial and total densities of states. In addition, we computed a variety of optical spectra, including the complex dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity, and electron energy loss function. The results demonstrate that a decrease in the bandgap leads to an increase in the zero-frequency limit of the dielectric function The origins of the peaks and structures in the optical spectra were identified.

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SABER Saad Essaoud , Djamel ALLALI , Hatem Allaf, Abdelmadjid Bouhemadou, arah Chaba Mouna, Missoum Radjai, Yarub Al-Douri, Abdelhak Bedjaoui, Saad Bin-Omran, Rabah Khenata, , (2024-07-10), Electronic and optical characteristics of CaLiX3 (X = Cl, Br, I) perovskite compounds using the Tran–Blaha modified Becke–Johnson potential, Physica Scripta, Vol:99, Issue:8, pages:085935-085947, IOPscience

This study investigates copper oxide thin films synthesized via the sol-gel method and deposited onto glass substrates using spin coating. The aim was to enhance their properties for photovoltaic applications through optimization of annealing temperature and precursor solution molar concentration. We examined the effects of annealing temperature on the structural and optical properties [1, 2] of the films. Notably, films treated at 450°C exhibited increased absorbance. Subsequently, employing this optimized temperature, CuO thin films of varying molar concentrations were deposited under the same conditions. Structural analysis via X-ray diffraction revealed a polycrystalline nature with a monoclinic crystal structure for all samples. Optical characterization using UV-Visible-NIR spectrophotometry indicated high absorbance in the visible region for the films.

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Djamel ALLALI , Rabie AMARI , AMMAR Boukhari , ELHADJ Benrezgua , Chouia Rabah, ,(2024-05-06), Study of Structural and Optical Properties of Copper Oxide Thin Films Prepared by Sol–Gel Spin–Coating Method,Le 2ème colloque national de chimie (CNC2@2024) 6 - 7 mai 2024,Msila

The structural, elastic, and thermodynamic characteristics of the GaCaF3 and GaSrF3 halide perovskites have been predicted for the first time, using ab initio pseudopotential plane wave calculations. The equilibrium lattice parameters are in good agreement with previously documented results. Both compounds exhibit substantial thermodynamic and mechanical stability. The single-crystal and polycrystalline elastic properties and related properties have been examined. GaCaF3 exhibits higher hardness than GaSrF3. The temperature dependence of the lattice parameter, bulk modulus, volume thermal expansion coefficient, heat capacity, and Debye temperature, have been computed using ab initio calculations combined with the quasi-harmonic Debye model.

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SABER Saad Essaoud , Djamel ALLALI , Abdelhak Bedjaoui, Missoum Radjai, Saad Bin-Omran, Abdelmadjid Bouhemadou, Yarub Al-Douri, Rabah Khenata, , (2024-05-04), Ab initio predictions of pressure-dependent structural, elastic, and thermodynamic properties of GaMF3 (M = Ca, and Sr) halide perovskites, Solid State Communications, Vol:387, Issue:, pages:115532-115539, Elsevier

In this study, we employed the pseudopotential plane wave approach to examine the influence of the X atom (X = Be, Ca, or Sr) on the physical properties of isostructural chloroperovskites GaXCl3. The GGA-PBEsol functional was employed to simulate the exchange–correlation interactions. The computed equilibrium lattice parameters exhibit a high level of concordance with the existing theoretical findings. The cohesion energy and enthalpy of formation were computed to verify the energetic stability of the materials under consideration. The determined values of the single-crystal elastic constants (Cij) indicate that GaBeCl3 remains mechanically stable up to a hydrostatic pressure of 18 GPa. Similarly, GaCaCl3 preserves its stability up to 5 GPa, while GaSrCl3 remains mechanically stable up to 1.25 GPa. The projected Cij values were used to estimate several elastic moduli and related properties, including the shear and bulk moduli, sound wave speeds, Young's modulus, Poisson's ratio, and Debye temperature. The energy band structures of the studied compounds, as predicted by the HSE06 functional, demonstrate their wide bandgap semiconductor nature. Specifically, GaBeCl3 demonstrates an indirect bandgap of 3.828 eV, while GaCaCl3 reveals an indirect bandgap of 4.612 eV and GaSrCl3 has an indirect bandgap of 4.405 eV. The quasiharmonic Debye approach was employed to examine various thermal parameters, including the temperature dependence of the unit cell volume, bulk modulus, expansion coefficient, Debye temperature, isochoric and isobar heat capacities, Grüneisen parameter, and entropy function. It has been shown that GaBeCl3 demonstrates a lower thermal expansion coefficient and a higher Debye temperature in comparison to GaCaCl3 and GaSrCl3.

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SABER Saad Essaoud , Djamel ALLALI , Missoum Radjai, Abdelmadjid Bouhemadou,, Abdelhak Bedjaoui,, Saad Bin-Omran, Rabah Khenata, Yarub Al-Douri, , (2024-05-03), Computational investigation of the structural, elastic, electronic, and thermodynamic properties of chloroperovskites GaXCl3 (X = Be, Ca, or Sr) using DFT framework, Physica Scripta, Vol:99, Issue:6, pages:065917-065935, IOPscience

A comprehensive examination of the crystal structure, as well as elastic and thermal properties, of the recently created Zintl phase CsGaSb2 has been carried out using ab initio density functional theory pseudo-potential plane-wave calculations. All the provided facts presented are newly forecasted, with the exception of the structural properties under normal conditions. The calculated lattice parameters and interatomic bond lengths of the investigated material closely correspond to the actual values, indicating a high level of accuracy. Forecasts have been generated for the elastic parameters and related characteristics of both single-crystal and polycrystalline phases of CsGaSb2. The parameters encompassed in this list are elastic constants, shear modulus, bulk modulus, Poisson’s ratio, Young’s modulus, anisotropy indices, elastic wave velocities, Pugh’s criterion, and Debye temperature. The mechanical and dynamic stability of CsGaSb2 as well as its elastic anisotropy have been established. The temperature dependence of various macroscopic properties, including bulk modulus, unit cell volume, volumetric thermal expansion coefficient, isochoric and isobaric thermal capacities, Debye temperature, Grüneisen parameter, and entropy function, was evaluated at specific pressures using Debye’s quasi-harmonic approach in combination with ab initio calculations.

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SABER Saad Essaoud , MOHAMMED ELAMIN KETFI , Djamel ALLALI , Sumayah Al-Essa, Abdelmadjid Bouhemadou, Saad Bin-Omran, Abdullah Chik, Missoum Radjai, Rabah Khenata, Yarub Al-Douri, , (2024-04-22), A Comprehensive Ab Initio Study of the Recently Synthesized Zintl Phase CsGaSb2 Structural, Dynamical Stability, Elastic and Thermodynamic Properties, Journal of Inorganic and Organometallic Polymers and Materials, Vol:34, Issue:9, pages:4174–4191, Springer

First-principles calculations employing the density functional theory full-potential (linearized) augmented planewave plus local orbitals (FP-(L)/APW + lo) method were conducted to investigate the structural, electronic and optical characteristics of silver-based ternary oxides XAgO (X = Li, Na, K, and Rb). The GGA-PBEsol and TB-mBJ functionals were employed to describe the exchange-correlation potential. The optimized lattice parameters and atomic positions obtained from the calculations exhibit good agreement with both theoretical predictions and experimental measurements. Various exchange-correlation functionals were employed to evaluate the electronic properties, revealing that the newly developed Tran–Blaha modified Becke–Johnson functional yields a significant improvement in the band gap value. All XAgO compounds under consideration are categorized as semiconductor materials where the band gap value decreases as the atomic size of the X element increases. The study also explored the total and site-projected l-decomposed densities of states. Additionally, the complex dielectric function, refractive index, extinction coefficient, reflectivity, and loss function spectra were calculated for the incident radiation polarized parallel to both the [100] and [001] crystalline directions. The interband transitions that contribute effectively to the observed peaks in the imaginary part of the dielectric function were identified.

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Djamel ALLALI , SABER Saad Essaoud , Bahri DEGHFEL , Abdelmadjid Bouhemadou, , (2024-01-04), A first-principles investigation on the structural, electronic and optical characteristics of tetragonal compounds XAgO (X= Li, Na, K, Rb), Computational Condensed Matter, Vol:38, Issue:38, pages:e00876, Elsevier

In this study, we conducted an ab initio investigation of the structural, elastic, electronic and optical properties of BaLiCl3halide perovskite. Our findings suggest that this material exhibit a high degree of stability in the cubic structure, with optimized lattice parameters that agree well with previous theoretical predictions. We estimated the monocrystalline elastic constants (Cij) for this compound via the strain-stress method.Using the predicted Cij values, we were able to deduce various elastic moduli for BaLiCl3 polycrystalline aggregates, including bulk modulus, Young's modulus, shear modulus, Lame coefficients, Poisson's ratio, and Debye temperature. Band structure, density of states and band gap pressure coefficients are also given. Our calculations show that our compound have an indirect band gap.We present calculationsof the frequency-dependent complex dielectric function ε(ω). We find that the values of zero-frequencylimit ε_1 (0) increase with decreasing the energy band gap. The origin of the peaks and structures in theoptical spectra is determined in terms of the calculated energy band structures. We hope that our study provides valuable insights into the structural, elastic, electronic and optical properties of ourperovskite compound that may be reference data for future investigations of these materials.

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Djamel ALLALI , ,(2023-12-09), structural, elastic, electronic and optical properties of BaLiCl3 perovskites: ab initio exploration,the Second Edition of the national Seminar entitled: ENVIRONNEMENT & GESTION DURABLE (HYBRID-SNEGD’23),Relizane-ALGERIA

In this work, the Cambridge Serial Total Energy Package CASTEP within Density Functional Theory (DFT) is used to study the structural and electronic properties of cubic silver based perovskite AgXCl3 (X= Be; space group pm-3m (221)). The structural investigation reveals the stability of these compounds. The band structure and density of states indicates the semiconducting nature of the compound.The study reveals the potential as candidates for optoelectronic devices.

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AMMAR Boukhari , Rabie AMARI , Djamel ALLALI , Bahri DEGHFEL , ,(2023-12-02), Structural and electronic properties of AgBeCl3 Perovskites: DFT based First-principles calculations,THE 1ST NATIONAL CONFERENCE ON PHYSICS AND IT’S APPLICATIONS,BOUSAADA

In this study, we conducted an ab initio investigation of the structural,electronic and optical properties of AgBaBr3Ag-based halide perovskites.using the full-potential linearized augmented plane-wave (FP-LAPW+lo) methodbasis set as implemented in the WIEN2k code .Calculated structural parameters, including thelattice constants(a),bulk modulus (B) and its pressure derivative (B'), for the considered compounds using both the local density (LDA) and generalized gradient approximations (GGA–PBEsol) are consistent with the available data in the scientific literature. To calculate the electronic properties, the exchange-correlation potential is treated with various functionals, and we find that the newly developed Tran–Blaha-modified Becke–Johnson (TB-mBJ) functional significantly improves the band gap.Band structure, total and site-projected l-decomposed densities of states, charge-carrier effective masses, charge transfers and charge density distribution maps were obtained; analyzed and compared with the available theoretical data. The frequency-dependent complex dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity and electron energy loss function spectra were calculated. The origins of the peaks and structures in the optical spectra are determined in terms of the calculated energy band structures.

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Djamel ALLALI , ,(2023-12-02), Electronic and optical properties of of AgBaBr3 Perovskites: An ab initio study with the Tran–Blaha-modified Becke–Johnson density functional,THE 1ST NATIONAL CONFERENCE ON PHYSICS AND IT’S APPLICATIONS,BOUSAADA-ALGERIA

The electronic and optical properties of the GaCaF3 and GaSrF3fluoride perovskites were predected for the first time in detail, using the first-principles pseudopotentialplanewave(PP-PW) method as implemented in the Cambridge SerialTotal Energy Package (CASTEP) code.The calculated electronic band structures and density of states diagrams show that the studied compounds are wide direct bandgap semiconductors.The calculated bandgap energies are4.09 eV and 4.01 eV, respectively forGaCaF3 and GaSrF3.The optical spectra, such as dielectric function, refractive index, extinction coefficient, absorption coefficient, reflectivity, energy loss function and optical conductivity, were calculated.Both compounds exhibit a noticeable absorption in the ultraviolet range. This makes them very competitive for the UV light detector.

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Djamel ALLALI , ,(2023-12-02), First principle prediction of the electronic and optical properties of the GaMF3 (M = Ca, Sr) fluoride perovskites,THE 1ST NATIONAL CONFERENCE ON PHYSICS AND IT’S APPLICATIONS,BOUSAADA-ALGERIA

In this work, the Cambridge Serial Total Energy Package CASTEP within Density Functional Theory (DFT) is used to study the structuraland electricalproperties of cubic silver based perovskite AgXCl3 (X= Be; space group pm-3m (221)).The structural investigation reveals the stability of these compounds.The band structure and density of states indicates the semiconducting nature of the compound.The study reveals the potential as candidates for optoelectronic devices.

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Djamel ALLALI , ,(2023-12-02), Structural and electrical properties of AgBeCl3 Perovskites: DFT based First-principles calculations,THE 1ST NATIONAL CONFERENCE ON PHYSICS AND IT’S APPLICATIONS,BOUSAADA-ALGERIA

In this comprehensive investigation, we undertook an ab initio exploration of the pressure-dependent structural, elastic and thermodynamic attributes of Be-Based fluoroperovskite compounds XBeF3 (X = K, Rb). Our analytical approach encompassed a diverse set of parameters, and the main conclusions and implications of our study are summarized as follows: (i) Calculated values of formation enthalpy and cohesion energy were determined for these perovskite compounds. Our results notably affirm the structural and thermodynamic stability of these materials in their cubic lattice configuration. (ii) Our optimized network parameters, derived from ab initio calculations, demonstrated commendable congruence with previously established theoretical predictions. This agreement strengthens the credibility of our conclusions. (iii) Using strain-constraint methodology, we successfully estimated the single-crystal elastic constants (Cij) of these compounds. This data served as the basis for further analysis. (iv) Using the obtained Cij values, we calculated a complete suite of elastic moduli for XBeF3 (X = K, Rb) in polycrystalline aggregates. This encompassed bulk modulus, Young’s modulus, shear modulus, Lame coefficients, Poisson’s ratio and Debye temperature, thus providing valuable information on the mechanical behavior of materials. (v) Using Debye’s quasi-harmonic approach, we systematically investigated the temperature dependencies of several essential thermodynamic properties. These include the lattice parameter, thermal expansion coefficient, bulk modulus, Debye temperature, and isochoric and isobaric heat capacities. These analyzes covered a wide temperature range while maintaining fixed selected pressures. Overall, our study aims to provide the scientific community with a robust and comprehensive dataset regarding the structural, elastic, and thermodynamic attributes of our perovskite compounds.

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Djamel ALLALI , ,(2023-12-02), Physical properties of Be-Based fluoroperovskite compounds XBeF3 (X = K, Rb): a first-principles study,THE 1ST NATIONAL CONFERENCE ON PHYSICS AND IT’S APPLICATIONS,BOUSAADA-ALGERIA

The study successfully produced ZnO and ZnO nanoparticles doped with transition metals (TMZO-NPs) using the coprecipitation method. Various properties of these nanoparticles were examined, including their structure, morphology, electronic behavior, optical characteristics, vibrations, and photocatalytic abilities. The analysis confirmed that all nanoparticles possessed a hexagonal wurtzite crystalline structure, with particle size being influenced by the presence of transition metals (Al, Ag, Cu, Mn). The particles exhibited a preference for orientation along the (002) axis. The shift in peak positions towards higher angles suggested that the TM might replace Zn ions in the ZnO lattice. The surface structure of the nanoparticles displayed a combination of spherical and hexagonal shapes. Further analysis identified important bands related to the stretching modes of TM-O and Zn–O bonds. The absorption properties and edges were also affected by the presence of TM. In the degradation study, both pure ZnO and TMZO-NPs were tested for their ability to break down methylene blue (MB) under UV light exposure for 90 min. Among the nanoparticles, Al-doped ZnO (AlZO-NPs) demonstrated the highest degradation efficiency, achieving 97.14% removal of MB within the given exposure time. The photocatalytic process followed a pseudo-first-order kinetics, indicating a strong correlation. This suggests that AlZO-NPs hold promise as a material for use in photocatalytic applications.

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Djamel ALLALI , , (2023-11-24), Coprecipitation synthesis of transition metal (Al, Mn, Cu, Ag) doped zinc oxide nanopowders: characterization, photocatalytic test, and comparison study, Journal of the Australian Ceramic Society, Vol:2023, Issue:, pages:1-10, Springer

We used the pseudopotential plane wave approach, as implemented in the Quantum Espresso program, to investigate the impact of X atoms (V, Nb, and Ta) on the physical properties of LuXCo2Sb2 double half Heusler alloys. We determined the equilibrium structural parameters, including the crystal lattice parameters, atomic position coordinates, and bulk modulus, with and without including the spin-orbit effects. The predicted singlecrystal elastic constants (Cij) show that the title compounds are mechanically stable with a pronounced elastic anisotropy. The bulk modulus, shear modulus, Young’s modulus, Poisson coefficient, Debye temperature, and Vickers hardness coefficient were deduced from Cij via the Voigt-Reuss-Hill approximations. We also determined the variations of some macroscopic physical parameters as functions of temperature and pressure, namely the thermal expansion coefficient, lattice thermal conductivity, heat capacity at constant volume, Debye temperature and entropy. The considered alloys demonstrate special thermal properties under pressure and heat conditions, specifically, their low thermal expansion coefficient and lattice thermal conductivity; their thermal expansion coefficient is lower than 4.5 × 10􀀀 5 K􀀀 1 at 1000 K, and lattice thermal conductivity don’t exceed 1 W.m􀀀 1 K􀀀 1 for temperatures higher than 300 K. Furthermore, we investigated the temperature and charge carrier concentration dependencies of some thermoelectric coefficients. The results of this study reveal the potential of the considered compounds for achieving a figure of merit greater than 0.5 at a temperature of 500 K and a doping concentration of 1020 cm􀀀 3.

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Djamel ALLALI , SABER Saad Essaoud , MOHAMMED ELAMIN KETFI , Abdelmadjid Bouhemadou, , (2023-11-14), First-principles analysis of the structural, thermodynamic, elastic and thermoelectric properties of LuXCo2Sb2 (X = V, Nb and Ta) double half Heusler alloys, Inorganic Chemistry Communications, Vol:159, Issue:, pages:111733, Elsevier

In this study, we used the ab-initio computational tools as implemented in the CASTEP code to explore the effects of pressure on the structural, elastic, electronic, thermodynamic and optical properties of the fluoroperovskite compounds XBeF3 (X = K, Rb) based on Being. Exchange–correlation interactions were modeled using the GGA-PBEsol functional. The ground state of the title materials was characterized by calculating the optimized lattice parameter, the bulk modulus B and its pressure derivative, and the Goldsmith tolerance factor. These materials exhibit structural stability in the cubic structure even when subjected to significant pressure levels, extending up to 18 GPa. The analysis of numerical assessments of single-crystal elastic constants (Cij), polycrystalline elastic moduli, namely shear modulus (G), Young’s modulus and Poisson’s ratio, as well as the anisotropy factor (A), highlights the mechanical stability, elastic anisotropy and ductility of considered the compounds. The thermodynamic properties of these materials were studied through the Debye quasi-harmonic model. Analysis of energy band structures and density of states spectra shows that XBeF3 (X = K, Rb) is insulating in nature, with band gaps of 7.99 and 7.26 eV, respectively. Additionally, we calculated the linear optical spectra, including dielectric function, absorption coefficient, refractive index, optical reflectivity, and energy loss function. Based on the results obtained, these materials could be used in various optoelectronic devices operating in the UV spectrum and in energy storage devices.

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Djamel ALLALI , SABER Saad Essaoud , Sarah Chaba Mouna1, Missoum Radjai, Abdelmadjid Bouhemadou, , (2023-11-03), Physical properties of Be-based fluoroperovskite compounds XBeF3 (X = K, Rb): a first-principles study, Journal of Physics: Condensed Matter, Vol:36, Issue:, pages:055701, IOPscience

In this comprehensive investigation, we undertook an ab initio exploration of the pressure-dependent structural, elastic and thermodynamic attributes of lithium-based halide perovskite compounds, namely CaLiCl3, CaLiBr3 and CaLiI3. Our analytical approach encompassed a diverse set of parameters, and the main conclusions and implications of our study are summarized as follows: (i) Calculated values of formation enthalpy and cohesion energy were determined for these perovskite compounds. Our results notably affirm the structural and thermodynamic stability of these materials in their cubic lattice configuration. (ii) Our optimized network parameters, derived from ab initio calculations, demonstrated commendable congruence with previously established theoretical predictions. This agreement strengthens the credibility of our conclusions. (iii) Using strain-constraint methodology, we successfully estimated the single-crystal elastic constants (Cij) of these compounds. This data served as the basis for further analysis. (iv) Using the obtained Cij values, we calculated a complete suite of elastic moduli for CaLiX3 (X = Cl, Br and I) in polycrystalline aggregates. This encompassed bulk modulus, Young’s modulus, shear modulus, Lame coefficients, Poisson’s ratio and Debye temperature, thus providing valuable information on the mechanical behavior of materials. (v) Using Debye’s quasi-harmonic approach, we systematically investigated the temperature dependencies of several essential thermodynamic properties. These include the lattice parameter, thermal expansion coefficient, bulk modulus, Debye temperature, and isochoric and isobaric heat capacities. These analyzes covered a wide temperature range while maintaining fixed selected pressures. Overall, our study aims to provide the scientific community with a robust and comprehensive dataset regarding the structural, elastic, and thermodynamic attributes of CaLiX3 perovskite compounds.

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Djamel ALLALI , SABER Saad Essaoud , Hatem Allaf, Missoum Radjai, Abdelmadjid Bouhemadou, , (2023-10-08), Ab initio predictions of pressure-dependent structural, elastic, and thermodynamic properties of CaLiX3 (X = Cl, Br, and I) halide perovskites, Computational Condensed Matter, Vol:37, Issue:, pages:e00850, Elsevier

The present research utilizes ab initio computations to examine the thermodynamic, structural, and elastic characteristics of XAgO ternary oxides, where X signifies Li, Na, K, and Rb.The GGA-PBE and GGA-WC functionals were used to calculate the ground-state lattice parameters and atomic position coordinates of the title materials. The calculated results were in good agreement with both experimental measurements and theoretical predictions. This suggests that the GGA-PBE and GGA-WC functionals are accurate for describing the structural properties of the material under study.This study offers computational predictions for the elastic properties of monocrystalline structures and polycrystalline aggregates of XAgO compounds. These predictions encompass various key parameters, including single-crystal elastic constants, Young's modulus, bulk modulus, Lame coefficients, Poisson's ratio, shear modulus, and Debye temperature. Additionally, the quasi-harmonic Debye approximation is utilized to explore the temperature-dependent behavior of bulk modulus, Debye temperature, volume thermal expansion coefficient, and isobaric and isochoric heat capacities over an extensive temperature range, while maintaining constant pressures. The results obtained from this model are found to be highly successful in accurately predicting the behavior of these properties.

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Djamel ALLALI , Rabie AMARI , AMMAR Boukhari , Bahri DEGHFEL , SABER Saad Essaoud , Abdelmadjid Bouhemadou, Saad Bin-Omran, Missoum Radjai, Rabah Khenata, Yarub Al-Douri, , (2023-10-04), Ab initio investigation of structural, elastic, and thermodynamic characteristics of tetragonal XAgO compounds (X = Li, Na, K, Rb), Physica Scripta, Vol:98, Issue:11, pages:115905, IOPscience

The present research utilizes ab initio computations to examine the thermodynamic, structural, and elastic characteristics of XAgO ternary oxides, where X signifies Li, Na, K, and Rb.The GGA-PBE and GGA-WCfunctionals were used to calculate the ground-state lattice parameters and atomic position coordinates of the title materials. The calculated results were in good agreement with both experimental measurements and theoretical predictions. This suggests that the GGA-PBE and GGAWCfunctionals are accurate for describing the structural properties of the material under study.This study offers computational predictions for the elastic properties of monocrystalline structures and polycrystalline aggregates of XAgO compounds. These predictions encompass various key parameters, including single-crystal elastic constants, Young’s modulus, bulk modulus, Lame coefficients, Poisson’s ratio, shear modulus, and Debye temperature. Additionally, the quasi-harmonic Debye approximation is utilized to explore the temperature-dependent behavior of bulk modulus, Debye temperature, volume thermal expansion coefficient, and isobaric and isochoric heat capacities over an extensive temperature range, while maintaining constant pressures. The results obtained from this model are found to be highly successful in accurately predicting the behavior of these properties.

Citation

Djamel ALLALI , AMMAR Boukhari , Rabie AMARI , Bahri DEGHFEL , SABER Saad Essaoud , Bouhemadou Abdelmadjid, , (2023-10-04), Ab initio investigation of structural, elastic, and thermodynamic characteristics of tetragonal XAgO compounds (X = Li, Na, K, Rb), Physica scripta, Vol:98, Issue:, pages:115905, IOPscience

The primary objective of this study is to investigate the influence of spin-orbit coupling and atom type on the electronic, optical, and thermoelectric properties of LuXNi2Sn2 (X = V, Nb, and Ta) double-half Heusler alloys. To achieve this, calculations were performed using the full potential linearized augmented plane wave method within the framework of density functional theory. Both full relativistic and scalar relativistic calculations were employed. The exchange-correlation interactions in this study were modeled using the PBEsol version of the generalized gradient approximation when calculating the structural ground state parameters. For the analysis of electronic, optical, and thermoelectric properties, the modified Becke–Johnson potential was employed. The modified Becke–Johnson potential was specifically chosen for its capability to improve the description of band gaps, particularly for systems with small band gaps, such as the LuXNi2Sn2 (X = V, Nb, and Ta) doublehalfn Heusler materials examined in this study. This potential offers a more accurate representation of the electronic properties, enabling a more reliable analysis of the optical and thermoelectric characteristics of the materials under investigation. The examined LuXNi2Sn2(X = V, Nb, and Ta) materials exhibit semiconductor behaviour, with band gaps smaller than 0.4 eV that can be controlled by varying the “X” atom. The charge carriers, specifically holes and electrons, exhibit light effective masses, indicating high mobility. Furthermore, these compounds exhibit low thermal expansion coefficients and satisfy the criteria for thermodynamic stability. In terms of optical properties, they display substantial absorption coefficients in the ultraviolet (UV) light region, high optical conductivity, and high reflectivity in the visible light region. Considering their favourable power factor and figure of merit characteristics, the LuXNi2Sn2 (X = V, Nb, and Ta) materials possess the potential to be promising candidates for thermoelectric applications.

Citation

Djamel ALLALI , , (2023-09-27), An Ab Initio Investigation of the Structural Stability, Thermodynamic, Optoelectronic, and Thermoelectric Properties of LuXNi2Sn2 (X = V, Nb, Ta) Double Half Heusler Materials, Journal of Inorganic and Organometallic Polymers and Materials, Vol:690, Issue:, pages:1-18, Springer

The primary objective of this study is to investigate the influence of spin-orbit coupling and atom type on the electronic, optical, and thermoelectric properties of LuXNi2Sn2 (X = V, Nb, and Ta) double-half Heusler alloys. To achieve this, calculations were performed using the full potential linearized augmented plane wave method within the framework of density functional theory. Both full relativistic and scalar relativistic calculations were employed. The exchange-correlation interactions in this study were modeled using the PBEsol version of the generalized gradient approximation when calculating the structural ground state parameters. For the analysis of electronic, optical, and thermoelectric properties, the modified Becke–Johnson potential was employed. The modified Becke–Johnson potential was specifically chosen for its capability to improve the description of band gaps, particularly for systems with small band gaps, such as the LuXNi2Sn2 (X = V, Nb, and Ta) double-half Heusler materials examined in this study. This potential offers a more accurate representation of the electronic properties, enabling a more reliable analysis of the optical and thermoelectric characteristics of the materials under investigation. The examined LuXNi2Sn2 (X = V, Nb, and Ta) materials exhibit semiconductor behaviour, with band gaps smaller than 0.4 eV that can be controlled by varying the “X” atom. The charge carriers, specifically holes and electrons, exhibit light effective masses, indicating high mobility. Furthermore, these compounds exhibit low thermal expansion coefficients and satisfy the criteria for thermodynamic stability. In terms of optical properties, they display substantial absorption coefficients in the ultraviolet (UV) light region, high optical conductivity, and high reflectivity in the visible light region. Considering their favourable power factor and figure of merit characteristics, the LuXNi2Sn2 (X = V, Nb, and Ta) materials possess the potential to be promising candidates for thermoelectric applications.

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SABER Saad Essaoud , MOHAMMED ELAMIN KETFI , Djamel ALLALI , Abdelmadjid Bouhemadou, Missoum Radjai, Saad Bin-Omran, , (2023-09-27), An Ab Initio Investigation of the Structural Stability, Thermodynamic, Optoelectronic, and Thermoelectric Properties of LuXNi2Sn2 (X = V, Nb, Ta) Double Half Heusler Materials, Journal of Inorganic and Organometallic Polymers and Materials, Vol:34, Issue:2, pages:885–902, Springer

In the present study, transition metal Al-doped ZnO nanoparticles (TM-ZN NPs) were synthesized via the chemical co-precipitation method. The structural, morphological, electronic, optical, vibrational as well as the photocatalytic properties of the elaborated TMZO-NPs, are then investigated. Hexagonal wurtzite crystallinity of all elaborated NPs is confirmed by the phase analysis and particle size is found to be affected by TM doping. XRD peak shows that all samples prefer orientation along (002) axis and TM (Al) may substitute ZnO structure as the peaks shift toward higher angles. The surface morphology of all samples exhibits mixture of spheroid-like and hexagon-like shaped structures. FTIR analyses are carried out to identify the important bands attributed to TM-O and Zn-O stretching vibration modes. The absorption intensity and edge are found affected by adding TM dopant. Degradation by pure ZnO and TMZO NPs of the methylene blue is investigated after 90 min UV light exposure. TM dopant affects the degradation of MB dye, where a high percentage (97.14%) being achieved after reasonable time of exposure (90 min) under UV light for Aluminum doped ZnO nanoparticles (AlZO NPs).

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Rabie AMARI , ELHADJ Benrezgua , Bahri DEGHFEL , AMMAR Boukhari , Djamel ALLALI , Siassi A, ,(2023-08-16), Studies on photocatalytic performance applications of undoped and Al-doped ZnO nanoparticles,NANO-2023,Bukovel, UKRAINE

In this study, we conducted an ab initio investigation of the structural, electronic and optical properties of AgCaBr3 and AgSrBr3 Calcium-based halide perovskites. using the full-potential linearized augmented plane-wave (FP-LAPW+lo) method [1] basis set as implemented in the WIEN2k code [2].Calculated structural parameters, including the lattice constants (a), bulk modulus (B) and its pressure derivative (B'), for the considered compounds using both the local density (LDA) [3] and generalized gradient approximations (GGA–PBEsol) [4] are consistent with the available data in the scientific literature. To calculate the electronic properties, the exchange-correlation potential is treated with various functionals, and we find that the newly developed Tran–Blaha-modified Becke–Johnson (TB-mBJ) [5–7] functional significantly improves the band gap. Band structure, total and site-projected l-decomposed densities of states, charge-carrier effective masses, charge transfers and charge density distribution maps were obtained; analyzed and compared with the available theoretical data. The frequency-dependent complex dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity and electron energy loss function spectra were calculated. The origins of the peaks and structures in the optical spectra are determined in terms of the calculated energy band structures.

Citation

Djamel ALLALI , Rabie AMARI , Bahri DEGHFEL , AMMAR Boukhari , ,(2023-08-16), Electronic and optical properties of of AgXBr3 (X = Ca and Sr) Perovskites: An ab initio study with the Tran–Blaha-modified Becke–Johnson density functional,NANO-2023,Bukovel, UKRAINE

In this study, we conducted an ab initio investigation of the structural, electronic and optical properties of AgCaBr3 and AgSrBr3 Calcium-based halide perovskites. using the full-potential linearized augmented plane-wave (FP-LAPW+lo) method [1] basis set as implemented in the WIEN2k code [2].Calculated structural parameters, including the lattice constants (a), bulk modulus (B) and its pressure derivative (B'), for the considered compounds using both the local density (LDA) [3] and generalized gradient approximations (GGA–PBEsol) [4] are consistent with the available data in the scientific literature. To calculate the electronic properties, the exchange-correlation potential is treated with various functionals, and we find that the newly developed Tran–Blaha-modified Becke–Johnson (TB-mBJ) [5–7] functional significantly improves the band gap. Band structure, total and site-projected l-decomposed densities of states, charge-carrier effective masses, charge transfers and charge density distribution maps were obtained; analyzed and compared with the available theoretical data. The frequency-dependent complex dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity and electron energy loss function spectra were calculated. The origins of the peaks and structures in the optical spectra are determined in terms of the calculated energy band structures. 1. Cottenier S. Density Functional Theory and the Family of (L)APW-methods: aStep-by-step Introduction // Instituut voor Kern-en Straling sfysica, KU Leuven, Belgium 4,second ed., ISBN-2002-2013.-978-90.- P. 807215-807222. 2. Blaha P., Schwarz K., Madsen G., Kvasnicka D., Luitz J. WIEN2k:An Augmented Plane Wave Plus Local Orbitals Program for Calculating Crystal Properties // Vienna University of Technology, Institute of Materials Chemistry Getreidemarkt, Vienna, Austria-2017.- 9/165-TC A-1060. 3. Perdew J.P., Wang Y. Accurate and simple analytic representation of the electron-gas correlation energy // Phys. Rev. B-1992.-45.- P. 13244-13249. 4. Perdew J.P., Ruzsinszky A., Csonka G.I., Vydrov O.A., Scuseria G.E., Constantin L.A., Zhou X., Burke, K. Restoring the Density-Gradient Expansion for Exchange in Solids and Surfaces // Phys. Rev. Lett.-2008.-100.- P. 136406-136410. 5. Becke A.D., Johnson E.R. A simple effective potential for exchange // J. Chem. Phys.-2006.-124.- P. 221101-221105. 6. Tran F., Blaha P., Schwarz K. Band gap calculations with Becke-Johnson exchange potential // J. Phys. Condens. Matter-2007.-19.- P.196208-1962016. 7. Tran F., Blaha P. Accurate Band Gaps of Semiconductors and Insulators with a SemilocalExchange-Correlation Potential // Phys. Rev. Lett.-2009.-102.- P. 226401-226405.

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Djamel ALLALI , ,(2023-08-16), Electronic and optical properties of of AgXBr3 (X = Ca and Sr) Perovskites: An ab initio study with the Tran–Blaha-modified Becke–Johnson density functional,NANO-2023,Bukovel, UKRAINE

Structural parameters, elastic constants and thermodynamic properties of the perovskite LiSrBr3, using density functional theory (DFT) based CASTEP (Cambridge Serial Total Energy Package) code with ultra-soft pseudo-potential USP plane wave and Perdew Burke Ernzerhof (PBE) exchange-correlation functional of Generalized Gradient Approximation (GGA), are reported. The optimized lattice parameters agree well with the available theoretical and experimental counterparts. Pressure dependence of the structural parameters is also explored. Pressure dependences of the single-crystal elastic constants Cij for LiSrBr3 are explored. The elastic wave velocities propagating along the principal crystallographic directions are numerically estimated. The elastic anisotropy is estimated and further illustrated by 3D-direction-dependent of the Young’s modulus. A set of some macroscopic elastic moduli, including the bulk, Young’s and shear moduli, Poisson’s coefficient, average elastic wave velocities and Debye temperature, were calculated for polycrystalline LiSrBr3 from the Cij via the Voigt-Reuss-Hill approximations. Through the quasiharmonic Debye model, which takes into account the phonon effects, the temperature and pressure dependencies of the bulk modulus, unit cell volume, volume thermal expansion coefficient, Debye temperature and volume constant and pressure constant heat capacities of LiSrBr3 are explored systematically in the ranges of 0 –20 GPa and 0 –1200 K

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Djamel ALLALI , ,(2023-06-24), Ab initio study of structural and thermodynamic properties of the cubic perovskite,6. INTERNATIONAL PALANDOKEN SCIENTIFIC STUDIES CONGRESS,ERZURUM / TURKEY

Zinc oxide is an important oxide semiconductor, with excellent physical and chemical properties that are used in different applications fields. In this research paper, ZnO thin films were synthesized using different types of solvent by sol-gel spin coating technique. The effect of solvent on the structural, morphological, photocurrent and optical properties of the films has been studied. X-ray diffraction revealed the high crystallinity of films in the wurtzite structure with a c-axis preferred orientation. SEM micrographs revealed that all films exhibit a fibrous structure, where the more homogeneous and dense surfaces were observed for ZnO-2-PrOH and ZnO– EtOH films. The optical properties analysis shows that the films have high transparency. Different structural and optical parameters were influenced by the type of solvent, where ZnO-2-PrOH film displays an improvement in structural and optical properties. The photoluminescence PL spectrum revealed three emissions, two green emissions and a UV emission at 390 nm. ZnO-2-PrOH film exhibits a high intensity ratio of UV to visible (IUV/ Ivis), a best UV response, and photocurrent properties. Finally, structural and optical parameters were also calculated by first-principles DFT calculations, discussed, and compared to those experimental.

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Djamel ALLALI , Abdelhafid MAHROUG , SAMIR Hamrit , , (2023-06-16), Optical, luminescence, photocurrent and structural properties of sol-gel ZnO fibrous structure thin films for optoelectronic applications: A combined experimental and DFT study, Optical Materials, Vol:142, Issue:, pages:114043, Elsevier

In this study, we conducted an ab initio investigation of the structural, elastic, electronic and optical properties of AgCaBr3 and AgCaF3 Calcium-based halide perovskites. Our findings suggest that these materials exhibit a high degree of stability in the cubic structure, with optimized lattice parameters that agree well with previous theoretical predictions. We estimated the monocrystalline elastic constants (Cij) for these compounds via the strain-stress method. Using the predicted Cij values, we were able to deduce various elastic moduli for AgCaBr3 and AgCaF3 polycrystalline aggregates, including bulk modulus, Young's modulus, shear modulus, Lame coefficients, Poisson's ratio, and Debye temperature. Band structure, density of states and band gap pressure coefficients are also given. Our calculations show that AgCaBr3 and AgCaF3 has an indirect band gap (R–Γ). We present calculations of the frequency-dependent complex dielectric function ε(ω). We find that the values of zero-frequency limit ε_1 (0) increase with decreasing the energy band gap. The origin of the peaks and structures in the optical spectra is determined in terms of the calculated energy band structures. We hope that our study provides valuable insights into the structural, elastic, electronic and optical properties of AgCaX3 perovskites compounds that may be reference data for future investigations of these materials.

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Djamel ALLALI , ,(2023-06-15), An ab initio study of the Structural, Elastic, Electronic and Optical Properties of AgCaX3 (X = Br, and F) Perovskites,the 4. INTERNATIONAL MEDITERRANEAN CONGRESS,Near East University and IKSAD Institute -TURKEY

In this study, we employed the ab initio pseudopotential plane wave approach, utilizing the GGAPBEsol exchange-correlation functional, to investigate the structural, elastic, and thermodynamic properties of BaXCl3 (X=Li, Na) perovskites under hydrostatic pressures ranging from 0 to 18 GPa. Apart from utilizing the GGA-PBEsol functional, this study also employed the GGA-PBE, GGA-WC, and LDA functionals to simulate the exchange-correlation interactions for computing the structural parameters. Our results show that the optimized lattice parameters are in good agreement with previously predicted values. Based on the calculated elastic moduli of a single crystal, we found that both BaLiCl3 and BaNaCl3 perovskites retain mechanical stability under hydrostatic pressures of up to 18 GPa. Furthermore, we calculated several other important parameters that describe the polycrystalline aggregates of these compounds, including the modulus of compressibility, the shear modulus, the Poisson’s ratio, Young’s modulus, the speeds of sound, and the Debye temperature. Additionally, we examined the temperature and pressure dependencies of the thermal coefficients of the perovskites using the quasi-harmonic approximation. Notably, all of the results presented in this study are reported for the first time and require further confirmation through experimental investigations.We hope that our findings contribute to a more comprehensive understanding of the structural and thermodynamic properties of BaXCl3 (X=Li, Na) perovskites under pressure.

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Djamel ALLALI , SABER Saad Essaoud , Sara Chaba Mouna, Missoum Radjai, Abdelmadjid Bouhemadou, , (2023-05-22), Structural, elastic, and thermodynamic properties of BaXCl3 (X = Li, Na) perovskites under pressure effect: ab initio exploration, Physica scripta, Vol:98, Issue:, pages:065949, IOPscience

In this study, we conducted an ab initio investigation of the pressure-dependent structural, elastic, and thermodynamic properties of CaLiCl3 lithium-based halide perovskites. Our findings suggest that these materials exhibit a high degree of stability in the cubic structure, with optimized lattice parameters that agree well with previous theoretical predictions. We estimated the monocrystalline elastic constants (Cij) for these compounds via the strain-stress method.Using the predicted Cij values, we were able to deduce various elastic moduli for CaLiCl3 polycrystalline aggregates, including bulk modulus, Young's modulus, shear modulus, Lame coefficients, Poisson's ratio, and Debye temperature. Additionally, we utilized the quasi-harmonic Debye approach to determine the temperature dependence of the volume thermal expansion coefficient, bulk modulus, Debye temperature, and isochoric and isobaric heat capacities over a wide temperature range at fixed selected pressures. We hope that our study provides valuable insights into the structural, elastic, and thermodynamic properties of CaLiCl3 perovskites compounds that may be reference data for future investigations of these materials.

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Djamel ALLALI , ,(2023-05-03), Ab Initio Predictions of Pressure-Dependent Structural, Elastic, and Thermodynamic Properties of CaLiCl3 Halide Perovskites,International Conference on Solar Energy and Hybrid Systems,laghouat-ALGERIA

Ab initio calculations based on density functional theory were performed to determine the structural parameters of the LuXCo2Sb2 (X = V, Nb and Ta) double half Heusler compounds and verify their thermodynamic stability in an orthorhombic structure as well as to predict their electronic and optical properties. The predicted electronic band structures show that LuVCo2Sb2, LuNbCo2Sb2, and LuTaCo2Sb2 are semiconductors with indirect bandgaps of 0.728, 0.845, and 0.898 eV, respectively. The effective masses calculated at the valence band maximum at the conduction band minimum show a strong anisotropy. It can be seen that electrons are lighter than holes. The nature of the electronic states involved in the formation of the energy bands has been determined thanks to the density of states calculations. The character of chemical bonds was analyzed through the charge density distribution map. Linear optical functions, namely complex dielectric function, absorption coefficient, optical reflectivity and refractive index, were calculated for all compounds in an energy range up to 20 eV. The calculated optical spectra exhibit a noticeable anisotropy. The compounds under consideration are characterized by strong absorption of incident electromagnetic radiation in a wide energy range.

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Djamel ALLALI , SABER Saad Essaoud , MOHAMMED ELAMIN KETFI , Abdelmadjid Bouhemadou, , (2023-03-15), Structural parameters, electronic structure and linear optical functions of LuXCo2Sb2 (X = V, Nb and Ta) double half Heusler alloys, Physica B: Condensed Matter, Vol:657, Issue:, pages:414809, Elsevier

First-principles calculations are carried out to investigate the structural and elastic properties for ScAuGe material, using density functional theory (DFT) based CASTEP (Cambridge Serial Total Energy Package) code with ultra-soft pseudo-potential USP plane wave and the local density approximation (LDA) correlation exchange. The optimized lattice parameters agree well with the available theoretical and experimental counterparts. Pressure dependence of the structural parameters is also explored.From the calculated elastic constants, we studied the mechanical stability for this material as well as their ductile/fragile behavior and their.A set of some macroscopic elastic moduli, including the bulk, Young’s and shear moduli, Poisson’s coefficient, average elastic wave velocities and Debye temperature, were calculated for polycrystalline ScAuGe from the Cij via the Voigt-Reuss-Hill approximations

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Djamel ALLALI , ,(2023-03-06), Examining computationally structural and elastic properties of the hexagonal material using DFT framework,THE 1ST NATIONAL CONFERENCE ON PHYSICS AND IT’S APPLICATIONS,BOUSAADA-ALGERIA

Ab initio full-potential (linearized) augmented plane-wave plus local orbitals (FP-(L)APW + lo) calculations are performed to study the hydrostatic pressure dependence of the mechanical and thermodynamics properties of GeMg2O4, GeZn2O4, and GeCd2O4 cubic spinels. The calculated equilibrium structural parameters using both the local density approximation and the generalized gradient approximation are well consistent with the available theoretical and experimental data in the literature. The monocrystalline elastic constants are predictet using the energy-strain scheme. The polycrystalline elastic moduli are determined from the monocrystalline elastic constants through the Voigt-Reuss-Hill approximations. To understand the mechanical behavior of the investigated compounds, assessments of their mechanical stability, ductility/brittleness, sound velocities, elastic anisotropy, pressure-dependent elastic constants, and Debye temperature are made. Regarding thermodynamic properties, temperature dependence of the lattice parameter, bulk modulus, isochoric and isobaric heat capacities, volume thermal expansion coefficient, and Debye temperature at different fixed pressures are explored through the quasi-harmonic Debye model coupled with the FP-(L)APW + lo approach.

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Djamel ALLALI , Bahri DEGHFEL , fares.zerarga@univ-bejaia.dz, abdelmadjid.bouhemadou@univ-setif.dz, , (2022), Ab initio study of the pressure dependence of mechanical and thermodynamic properties of GeB2O4 (B= Mg, Zn and Cd) spinel crystals, Computational Condensed Matter, Vol:32, Issue:, pages:e00705, Elsevier B.V.

Zn0.875Al0.125O nanoparticles are fabricated by a co-precipitation technique using zinc acetate dehydrate [Zn(CH3COO)2•2H2O] and aluminum nitrate nonahydrate(Al(NO3)39(H2O) as a starting material and doping source. X-ray diffraction, ultraviolet-visible spectroscopy and photoluminescence spectroscopy are employed to investigate the effect of Al doping on the structural, electronic and optical properties of ZnO nanoparticles. The obtained results are compared with those using first-principles calculation based on density functional theory (DFT) with local density approximation (LDA) plus Hubbard U (DFT–LDA+U) method. This latter represents the theoretical framework to deal with strongly correlated materials to predicted successfully the electronic properties of such materials.

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Djamel ALLALI , Rabie AMARI , Bahri DEGHFEL , ,(2022), Electronic, structural, magnetic and optical properties of of spinel compound MgFe2O4,10th International Conference on Materials Sciences And Technology, (MatScience-2022),khenchela, Algeria

We report ab initio density functional theory calculations of the structural, electronic and optical properties of Ag-based ternary oxides XAgO (X= Li and Na) using the full-potential linearized augmented plane-wave (FP-LAPW+lo) method [1] basis set as implemented in the WIEN2k code [2]. Calculated structural parameters, including the two lattice constants, (a) and (c), three internal coordinates, yX, xAg, and xO, bulk modulus (B) and its pressure derivative (B'), for the considered compounds using both the local density (LDA) [3] and generalized gradient approximations (GGA–PBEsol) [4] are consistent with the available data in the scientific literature. To calculate the electronic properties, the exchangecorrelation potential is treated with various functionals, and we find that the newly developed Tran–Blaha-modified Becke–Johnson (TB-mBJ) [5–7] functional significantly improves the band gap. Band structure, total and site-projected l-decomposed densities of states, charge-carrier effective masses, charge transfers and charge density distribution maps were obtained; analyzed and compared with the available theoretical data. The frequency-dependent complex dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity and electron energy loss function spectra were calculated with an incident radiation polarized parallel to both [100] and [001] crystalline directions. The origins of the peaks and structures in the optical spectra are determined in terms of the calculated energy band structures

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Djamel ALLALI , AMMAR Boukhari , Rabie AMARI , Fares ZERARGA, Abdelmadjid BOUHEMADOU, Khadidja BOUDIAF, ,(2022), Electronic and optical properties of Ag-based oxides XAgO (X= Li and Na): An ab initio study with the Tran–Blahamodified Becke–Johnson density functional,1st international conference on chemical matters and environment preservation IC-CMEP’22,Ouargla, Algeria

Structural parameters, elastic constants and thermodynamic properties of the tetragonal ternary Ag-based oxides LiAgO and NaAgO are investigated theoretically for the first time using the plane-wave ultra-soft pseudopotential method [1] based on the density functional theory [2,3]. The optimized lattice parameters and atomic positions agree well with the available theoretical and experimental counterparts. Pressure dependence of the structural parameters is also explored. Pressure dependences of the single-crystal elastic constants Cij for LiAgO and NaAgO are explored. The elastic wave velocities propagating along the principal crystallographic directions are numerically estimated. The elastic anisotropy is estimated and further illustrated by 3D-direction-dependent of the Young’s modulus. A set of some macroscopic elastic moduli, including the bulk, Young’s and shear moduli, Poisson’s coefficient, average elastic wave velocities and Debye temperature, were calculated for polycrystalline LiAgO and NaAgO from the Cij via the Voigt-Reuss-Hill approximations [4–6]. Through the quasiharmonic Debye model [7], which takes into account the phonon effects, the temperature and pressure dependencies of the bulk modulus, unit cell volume, volume thermal expansion coefficient, Debye temperature and volume constant and pressure constant heat capacities of LiAgO and NaAgO are explored systematically in the ranges of 0–20 GPa and 0–1200 K.

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Djamel ALLALI , Amari Rabie , Bahri DEGHFEL , AMMAR Boukhari , ,(2022), Structural, elastic and thermodynamic properties of Ag-based oxides XAgO (X = Li and Na): An ab initio study,10th International Conference “Nanotechnologies and Nanomaterials” (NANO-2022),Lviv. Ukraine

We report on the structural parameters and thermodynamic properties of the perovskite NaCaBr3 using the density functional theory (DFT) based CASTEP (Cambridge Serial Total Energy Package) code with the ultra-soft pseudo-potential USP plane wave and Perdew Burke Ernzerhof (PBE) exchange-correlation functional of the Generalized Gradient Approximation (GGA). The optimized lattice parameters agree well with the available theoretical and experimental counterparts. Pressure dependence of the structural parameters is also explored. Pressure dependences of the single-crystal elastic constants Cij for NaCaBr3 are explored. The elastic wave velocities propagating along the principal crystallographic directions are numerically estimated. The elastic anisotropy is estimated and further illustrated by 3D-direction-dependent of the Young’s modulus. A set of some macroscopic elastic moduli, including the bulk, Young’s and shear moduli, Poisson’s coefficient, average elastic wave velocities and Debye temperature, were calculated for polycrystalline NaCaBr3 from the Cij via the Voigt-Reuss-Hill approximations. Through the quasiharmonic Debye model, which takes into account the phonon effects, the temperature and pressure dependencies of the bulk modulus, unit cell volume, volume thermal expansion coefficient, Debye temperature and volume constant and pressure constant heat capacities of NaCaBr3 are explored systematically in the ranges of 0 –20 GPa and 0 –1200 K.

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Djamel ALLALI , ,(2022), Firstprinciples calculations to investigate structural and thermodynamic properties of the cubic perovskites NaCaBr3 compound,1st International Conference on Engineering, Natural and Social Sciences ICENSOS 2022,Konya, Turkey

Structural parameters, elastic constants and electronic properties of the perovskite LiSrBr3, using density functional theory (DFT) based CASTEP (Cambridge Serial Total Energy Package) code with ultra-soft pseudo-potential USP plane wave and Perdew Burke Ernzerhof (PBE) exchange-correlation functional of Generalized Gradient Approximation (GGA), are reported. The optimized lattice parameters agree well with the available theoretical and experimental counterparts. Pressure dependence of the structural parameters are also explored. Pressure dependences of the single-crystal elastic constants Cij for LiSrBr3 are explored. The elastic wave velocities propagating along the principal crystallographic directions are numerically estimated. The elastic anisotropy is estimated and further illustrated by 3D-direction-dependent of the Young’s modulus. A set of some macroscopic elastic moduli, including the bulk, Young’s and shear moduli, Poisson’s coefficient, average elastic wave velocities and Debye temperature, were calculated for polycrystalline LiSrBr3 from the Cij via the Voigt-Reuss-Hill approximations. The electronic band structure calculations reveal that LiSrBr3 has a direct. The finding of band gap is agreed well with the data that is already available. The degree of localized electrons in different bands is confirmed by partial density of states (PDOS) and total density of states (TDOS).

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Djamel ALLALI , ,(2022), First-principles calculations to investigate structural, elastic and electronic properties of the cubic perovskite LiSrBr3 under high,1st International Conference on Scientific and Academic Research,Konya, Turkey

Motivated by the growing demand for new performant semiconducting materials, we investigated in detail the structural, elastic, electronic and optical properties of two newly synthesized compounds, namely Tl2CdGeSe4 and Tl2CdSnSe4, using density functional theory calculations. The calculations were performed relativistically, including the spin–orbit coupling (SOC). The computed equilibrium structural parameters are in excellent agreement with available measurements. Note that the calculations of all the considered properties were performed with the theoretically obtained equilibrium lattice parameters. The predicted monocrystalline and polycrystalline elastic constants reveal that the studied compounds are soft, ductile, mechanically stable and substantially structurally and elastically anisotropic materials. Our calculations using the Tran-Blaha modified Becke-Johnson potential with the inclusion of SOC show that Tl2CdGeSe4 and Tl2CdSnSe4 are direct bandgap semiconductors. The inclusion of SOC is found to reduce the fundamental bandgap of Tl2CdGeSe4 from 1.123 to 0.981 eV and that of Tl2CdSnSe4 from 1.097 to 0.953 eV. The l-decomposed atom-projected densities of states were calculated to identify the contribution of each constituent atom to the electronic states in the energy bands. The upper valence subband predominantly comes from the Se-4p states, while the bottom of the conduction band mainly originates from the Se-4p and Ge-4p/Sn-5p states. The frequency-dependent linear optical parameters, viz., the complex dielectric function, absorption coefficient, refractive index, reflectivity and energy-loss function, were calculated for electromagnetic waves polarized parallel and perpendicular to the c-axis in a wide energy window. An attempt was made to identify the microscopic origin of the peaks and structures observed in the calculated optical spectra.

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Djamel ALLALI , Selma Karkour, Abdelmadjid Bouhemadou, , (2022), Structural, elastic, electronic and optical properties of the newly synthesized selenides Tl2CdXSe4 (X = Ge, Sn), THE EUROPEAN PHYSICAL JOURNAL B, Vol:95, Issue:38, pages:23, Springer

We report ab initio density functional theory calculations of the structural, electronic and optical properties of Ag-based ternary oxides MAgO (M= K and Rb) using the full-potential linearized augmented plane-wave (FP-LAPW+lo) method basis set as implemented in the WIEN2k code. Calculated structural parameters, including the two lattice constants, (a) and (c), three internal coordinates, yM, xAg, and xO, bulk modulus (B) and its pressure derivative (B'), for the considered compounds using both the local density (LDA) and generalized gradient approximations (GGA–PBEsol) are consistent with the available data in the scientific literature. To calculate the electronic properties, the exchange-correlation potential is treated with various functionals, and we find that the newly developed Tran–Blaha-modified Becke–Johnson (TB-mBJ) functional significantly improves the band gap. Band structure, total and site-projected l-decomposed densities of states, charge-carrier effective masses, charge transfers and charge density distribution maps were obtained; analyzed and compared with the available theoretical data. The frequency-dependent complex dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity and electron energy loss function spectra were calculated with an incident radiation polarized parallel to both [100] and [001] crystalline directions. The origins of the peaks and structures in the optical spectra are determined in terms of the calculated energy band structures.

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Djamel ALLALI , ,(2022), STRUCTURAL, ELECTRONIC AND OPTICAL PROPERTIES OF AG-BASED OXIDES MAGO (M= K AND RB): AN AB INITIO STUDY,International Conference on Global Practice of Multidisciplinqry Scientific Studies held,Turkey

Structural parameters, elastic constants and thermodynamic properties of the tetragonal ternary Ag-based oxides KAgO and RbAgO are investigated theoretically for the first time using the plane-wave ultra-soft pseudopotential method based on the density functional theory. The optimized lattice parameters and atomic positions agree well with the available theoretical and experimental counterparts. Pressure dependence of the structural parameters is also explored. Pressure dependences of the single-crystal elastic constants Cij for KAgO and RbAgO are explored. The elastic wave velocities propagating along the principal crystallographic directions are numerically estimated. The elastic anisotropy is estimated and further illustrated by 3D-direction-dependent of the Young’s modulus. A set of some macroscopic elastic moduli, including the bulk, Young’s and shear moduli, Poisson’s coefficient, average elastic wave velocities and Debye temperature, were calculated for polycrystalline KAgO and RbAgO from the Cij via the Voigt-Reuss-Hill approximations. Through the quasiharmonic Debye model, which takes into account the phonon effects, the temperature and pressure dependencies of the bulk modulus, unit cell volume, volume thermal expansion coefficient, Debye temperature and volume constant and pressure constant heat capacities of KAgO and RbAgO are explored systematically in the ranges of 0–20 GPa and 0–1200 K.

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Djamel ALLALI , ,(2022), FIRST PRINCIPLES INVESTIGATION ON THE STRUCTURAL, ELASTIC AND THERMODYNAMIC PROPERTIES OF AG-BASED OXIDES KAGO AND RBAGO AS A FUNCTION OF PRESSURE,THE 1ST INTERNATIONAL CONFERENCE ON RENEWABLE MATERIALS AND ENERGIES ICRME2022 October 26-27, 2022, OUARGLA-ALGERIA,OUARGLA-ALGERIA

We report ab initio density functional theory calculations of the structural, electronic and optical properties of the spinel oxides SiMg2O4, SiZng2O4, and SiCd2O4 using the full-potential linearized augmented planewave method[1] basis set as implemented in the WIEN2k code [2]. The structural parameters calculated using both the local density[3] and generalized gradient approximations [4]to the exchange-correlation potential are consistent with the literature data. To calculate the electronic properties, the exchange-correlation potential is treated with various functionals, and we find that the newly developed Tran–Blaha-modified Becke–Johnson[5–7] functional significantly improves the band gap. We predict a direct band gap in all of the considered SiB2O4 compounds, and the band gaps continuously decrease as the atomic size of the B element increases. The decrease in the fundamental direct band gap (Γ–Γ) from SiMg2O4 to SiZn2O4 to SiCd2O4 can be attributed to p–d mixing in the upper valence bands of SiZn2O4 and SiCd2O4. The lowest conduction band is well dispersive, similar to that found for transparent conducting oxides such as ZnO. This band is mainly defined by the s and p electrons of the Si and B(B =Mg, Zn, Cd) atoms. The topmost valence band is considerably less dispersive and is defined by O-2p and B–d electrons. The charge-carrier effective masses are evaluated at the topmost valence band and at the bottommost conduction band that were calculated. The frequency-dependent complex dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity and electron energy loss function were estimated.

Citation

Djamel ALLALI , ,(2022), Electronic and optical properties of the SiB2O4 (B = Mg, Zn, and Cd) spinel oxides: An ab initio study,the First national Seminar on Green Chemistry and Natural Products (GCNP’22), organized from March 14-15, 2022 at the University of Echahid Hamma Lakhdar, El-Oued,University of Echahid Hamma Lakhdar, El-Oued-ALGERIA

Electronic and thermoelectric properties of three principal representatives of the GeMg2O4, GeZn2O4 and GeCd2O4 cubic spinels compounds have been studied ab initio. We use the full-potential Linearized augmented plane-wave plus local orbitals method (FP-LAPW+lo) as implemented in the Wien2K code with the original TB-mBJ functional to model the exchange-correlation potential. Qualitatively, the investigated compounds show similar energy band dispersion; a direct band gap (Γ–Γ) was found for the three considered compounds. The FP-LAPW band structure calculation was profited to investigate the thermoelectric properties of the studied compound employing the BoltzTraP code which based on the semi-classical Boltzmann transport theory. The potential of the studied compounds as thermoelectric materials was evaluated at three fixed applied temperature (T=300, 500 and 700 K). According to the rigid band approximation, the calculated values of the Seebeck coefficient for the three doped compounds (ranged from 1016 to 1021 excess holes/electrons) decreases going from GeMg2O4 to GeZn2O4 to GeCd2O4, this is in accordance to the fact of decreasing the Seebeck coefficient with decreasing band gap. The thermoelectric efficiency was evaluated through calculating figure of merit ZT, we found that hole-doping are more favourable and enjoyed, the calculated values might be greater by reducing the lattice thermal conductivity.

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Djamel ALLALI , Fares ZERARGA, Abdelmadjid BOUHEMADOU, Khadidja BOUDIAF, ,(2020), Thermoelectric Properties of the GeX2O4 (X =Mg, Zn and Cd) cubic spinels compounds: An ab-initio FP-LAPW study.,La 1ère Conférence Nationale sur la Transition Energétique en Algérie CNTEA1-2020,Algérie

Electronicand thermoelectric properties of three principal representatives of the LiCdP, LiCdAs and LiCdSb filled-tetrahedral compounds have been studied ab initio. We use the full-potential Linearized augmented plane-wave plus local orbitals method (FP-LAPW+lo) as implemented in the Wien2K code with the original TB-mBJ functional to model the exchange-correlation potential. Qualitatively, the investigated compounds show similar energy band dispersion; indirect band gap Г-X was found for the three considered compounds. A combination between The FP-LAPW+lo band stucture and the semi-classical Boltzmann transport theory were used to investigate the thermoelectric properties, the potential of the studied compounds as thermoelectric materials at three applied temperature (i.e., T=300, 600 and 900 K) was assessed. The calculated values of the Seebeck coefficient (i.e., 265, 259 and 248 µV/K) decreases going from LiCdP to LiCdAs to LiCdSb, this can be attributed to the trend of semiconducting materials where Seebeck coefficient decreases with decreasing band gap. The thermoelectric efficiency was evaluated through calculating figure of merit ZT. Intrinsically, figure of merit is about 0.8, this value might be greater by tuning the electronic structure via hole-doping.

Citation

Djamel ALLALI , Foudil SAHNOUNE , Fares ZERARGA, Abdelmadjid BOUHEMADOU, Khadidja BOUDIAF, ,(2020), Thermoelectric Properties of the LiCdX (X =P, As and Sb)filled-tetrahedral compounds: An ab initio FP-LAPW study,La 1ère Conférence Nationale sur la Transition Energétique en Algérie CNTEA1-2020,Algérie

Ce cours de physique 1 (mécanique du point matériel) a été rédigé à l’intention des étudiants qui préparent, une licence dans les domaines des Sciences de la Matière et des Sciences et Technologies. Il est conforme au programme officiel. Le premier chapitre est consacré à des rappels sur l’algèbre vectorielle et l’analyse dimensionnelle. Les deux traitent des grandeurs physiques de base qui sont utilisées pour l’expression des lois physiques. En plus des rappels nécessaires, l’objectif de cette partie est d’introduire des définitions claires et des notations appropriées. Le deuxième chapitre est dédié à la cinématique. Son but est de décrire les mouvements d’objets sans s’intéresser aux causes qui les produisent. Il traite uniquement des mouvements de points matériels c’est-à-dire exclusivement des translations. Le troisième chapitre traite de la dynamique du point matériel, dans le cadre de la mécanique de Newton avec ses trois lois ou principes indissociables: la loi d’inertie, la loi fondamentale de la dynamique et la loi des actions réciproques. Nous y considérons les lois générales, dites lois de forces, établies pour un certain nombre d’interactions avec des applications destinées à la prévision des mouvements des corps. La notion de moment cinétique d’une particule par rapport à l’origine et celle des pseudo-forces y sont également traitées. Le quatrième chapitre concerne la troisième méthode d’analyse qui est celle du travail et de l’énergie. Cette approche élimine le calcul de l’accélération en reliant directement la force, la masse, la vitesse et le déplacement. Nous considérons d’abord le travail d’une force et l’énergie cinétique d’une particule. Nous traitons ensuite les notions d’énergies potentielle et totale que nous appliquons au principe de conservation de l’énergie dans diverses situations pratiques.

Citation

DjamelALLALI , ,(2020); Cours de Physique 1 MECANIQUE DU POINT MATERIEL,جامعة محمد بوضياف المسيلة,

We report ab-initio density functional theory calculations of the electronic and optical properties of the spinel oxides GeMg2O4, GeZng2O4 and GeCd2O4 using the full potential linearized augmented plane-wave method. To calculate the electronic properties, the exchange-correlation interaction was treated with various functionals. We find that the newly developed Tran–Blaha modified Becke–Johnson functional significantly improves the band gap value. All considered GeB2O4 compounds are direct band gap materials. The band gap value decreases with increasing atomic size of the B element. The decrease of the fundamental direct band gap (Γ–Γ) when one moves from GeMg2O4 to GeZn2O4 to GeCd2O4 can be attributed to the p–d mixing in the upper valence bands of GeZn2O4 and GeCd2O4. The lowest conduction band, which is mainly originated from the s and p states of the Ge and B (B = Mg, Zn, Cd) atoms, is well dispersive, similar to that of transparent conducting oxides such as ZnO. The topmost valence band, which is originated from the O-2p and B-d states, is considerably less dispersive. Optical spectra in a wide energy range from 0 to 30eV are provided and the origin of the observed peaks and structures are assigned. We find that the zero-frequency limit of the dielectric function increases with decreasing band gap value.

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Djamel ALLALI , Foudil SAHNOUNE , Abdelmadjid Bouhemadou, Fares Zerarga, , (2019), Electronic and Optical Properties of the Spinel Oxides GeB2O4(B = Mg, Zn and Cd): an Ab-initio Study, Journal of Nanoelectronics and Optoelectronics, Vol:14, Issue:1, pages:945-952, AMER SCIENTIFIC PUBLISHERS

Density functional FP-LAPW+‏lo method calculations were performed to explore the structural, electronic, optical, elastic, thermoelectric and thermodynamic properties of the spinel oxides ZnRh2O4 and CdRh2O4. The exchange-correlation potential were described using the GGA-PBEsol and TB-mBJ functionals. As the first step, the optimized structural parameters, including the lattice parameter and atomic coordinates, were determined. Electronic band structure, atomic-resolved l-projected densities of electronic states and photon energy dependence of the linear optical functions were computed. It is found that both investigated compounds are indirect band gap semiconductors. The band gap results from the splitting of the Rh : 4d6 states into occupied Rh : 4d - t_2g^6 states, which form the valence band maximum (VBM), and the empty states Rh : 4d-e_g^0, which form the conduction band minimum (CBM), owing to the octahedral substantial crystal-field. The electronic interband transitions responsible of the structures in the optical spectra were specified. Single-crystal and polycrystal elastic moduli, wave sound velocities, Debye temperature, Pugh's indicator and indexes of elastic anisotropy were numerically estimated using total energy versus strain. FP-LAPW‏+lo band structure in combination with the standard Boltzmann transport theory were employed to calculate the thermoelectric parameters, including Seebeck coefficient, electrical and thermal conductivities and figure of merit. It is found that the title compounds are potential candidates for thermoelectric applications if one can further reduce their thermal conductivities via some techniques. FP-LAPW+‏lo approach in combination with the quasi-harmonic Debye model was employed to study temperature and pressure dependences of some macroscopic physical parameters. Our obtained results in the present work are discussed in comparison with the available experimental and theoretical data. The calculated results show a good agreement with the available experimental and theoretical results.

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Djamel ALLALI , Abdelmadjid Bouhemadou, Khadidja Boudiaf, B. Al Qarni, Saad Bin-Omran, Rabah Khenata, Yarub Al-Douri, , (2019), Electronic, optical, elastic, thermoelectric and thermodynamic properties of the spinel oxides ZnRh2O4 and CdRh2O4, Journal of Alloys and Compounds, Vol:774, Issue:8, pages:299-314, ELSEVIER SCIENCE SA

Electronic and thermoelectric properties of three principal representatives of the LiZnP, LiZnAs and LiZnSb filled-tetrahedral compounds have been studied ab initio. We use the full-potential Linearized augmented plane-wave plus local orbitals method (FP-LAPW+lo) as implemented in the Wien2K code with the original TB-mBJ functional to model the exchange-correlation potential. Qualitatively, the investigated compounds show similar energy band dispersion; indirect band gap Г-X was found for the three considered compounds. A combination between The FP-LAPW+lo band stucture and the semi-classical Boltzmann transport theory were used to investigate the thermoelectric properties, the potential of the studied compounds as thermoelectric materials at three applied temperature (i.e., T=300, 600 and 900 K) was assessed. The calculated values of the Seebeck coefficient (i.e., 265, 259 and 248 µV/K) decreases going from LiZnP to LiZnAs to LiZnSb, this can be attributed to the trend of semiconducting materials where Seebeck coefficient decreases with decreasing band gap. The thermoelectric efficiency was evaluated through calculating figure of merit ZT. Intrinsically, figure of merit is about 0.8, this value might be greater by tuning the electronic structure via hole-doping.

Citation

Djamel ALLALI , Foudil SAHNOUNE , Fares ZERARGA, Abdelmadjid BOUHEMADOU, Khadidja BOUDIAF, ,(2019), Thermoelectric Properties of the LiZnX (X =P, As and Sb) filled-tetrahedral compounds: An ab initio FP-LAPW study,6thINTERNATIONAL CONFERENCE ON COMPUTATIONAL AND EXPERIMENTAL SCIENCE AND ENGINEERING (ICCESEN-2019),ANTALYA-TURKEY

Mullite (3Al2O3·2SiO2) as the main phase in SiO2- Al2O3 system is one of the most commun studied ceramic materials has low toughness and hardness, better thermal shock resistance, excellent high temperature mechanical properties, high thermal and chemical stability, low thermal expansion coefficient and high creep resistance. In this present study, Mullite of stoichiometric composition has been synthesized by sol-gel process followed by calcination. Tetraethyl orthosilicate TEOS as silica source and Aluminum nitrate nonahydrate Al(NO3)3.9H2O as alumina source. Thermogravimetry (TG), differential thermal analysis (DTA), dilatometry, high temperature x-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) complementary techniques were used to analyses the transformation of phases and sintering behaviour, The coefficient of thermal expansion (α) and investigate crystallization kinetics. Different crystalline phases were present in the samples sintered in the temperature range 900–1400 °C, the Mullite phase started to crystallize at 1100 °C, and the formation of highly dense Mullite (996%) was complete at 1350 °C. The activation energy values for Mullite formation calculated using Kissinger, Boswell, and Ozawa methods. The kinetic parameters n and m had values close to 2. Bulk nucleation with a constant number of nuclei was the dominant mechanism in cordierite crystallization, followed by two-dimensional growth controlled by interface reaction.

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Foudil SAHNOUNE , MENAD Heraiz , Djamel ALLALI , Smail lamara, Djaida Redaoui, Nouari Saheb, ,(2019), Phase transformation and Sintering of Mullite Powder Synthesized via Sol-Gel process Using Differential themal Analysis (DTA) and Dilatometry (DL),6th INTERNATIONAL CONFERENCE ON COMPUTATIONAL AND EXPERIMENTAL SCIENCE AND ENGINEERING (ICCESEN-2019),ANTALYA-TURKEY

We report ab-initio density functional theory calculations of the structural, electronic and optical properties of the spinel oxides GeMg2O4,GeZng2O4 and GeCd2O4 using the full-potential linearized augmented plane-wave method. The structural parameters calculated using both the local density and generalized gradient approximations to the exchange-correlation potential are consistent with the literature data. To calculate the electronic properties, the exchange-correlation potential is treated with various functionals, and we find that the newly developed Tran–Blaha-modified Becke–Johnson functional significantly improves the band gap. We predict a direct band gap in all of the considered GeB2O4 compounds, and the band gaps continuously decrease as the atomic size of the B element increases. The decrease in the fundamental direct band gap (Γ–Γ) from GeMg2O4 to GeZn2O4 to GeCd2O4 can be attributed to p–d mixing in the upper valence bands of GeZn2O4 and GeCd2O4. The lowest conduction band is well dispersive, similar to that found for transparent conducting oxides such as ZnO. This band is mainly defined by the s and p electrons of the Si and B (B = Mg, Zn, Cd) atoms. The topmost valence band isconsiderably less dispersive and is defined by O-2 pand B–d electrons. The charge-carrier effective masses are evaluated at the topmost valence band and at the bottommost conduction band that were calculated. The frequency-dependent complex dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity and electron energy loss function were estimated. We find that the value of the zero-frequency limit of the dielectric function ε(0) increases as the band gap decreases. The origins of the peaks and structures in the optical spectra are determined in terms of the calculated energy band structures.

Citation

Djamel ALLALI , Foudil SAHNOUNE , Abdelmadjid BOUHEMADOU, Fares ZERARGA, ,(2018), Electronic and Optical Properties Of The Spinel Oxıdes GeB2O4(B = Mg, Zn and Cd): An Ab-initio Study,5thINTERNATIONAL CONFERENCE ON COMPUTATIONAL AND EXPERIMENTAL SCIENCE AND ENGINEERING (ICCESEN-2018) 10-14October 2018,,ANTALYA-TURKEY

The structural, electronic and optical properties of three principal representatives of the LiZnP, LiZnAs and LiZnSb filled-tetrahedral compounds have been explored from first-principles (full-potential (Linearized) augmented plane-wave plus local orbitals method (FP-(L)APW+lo)). The structural parameters, including the lattice constant (a), the bulk modulus (B) and its pressure derivative (B') of the considered compounds are calculated using both the local density (LDA) and generalized gradient approximations (GGA) to the exchange-correlation potential are consistent with the literature data.The single crystal elastic constants are numerically estimated using total energy-strain approach with two different sets of distortions. The polycrystalline aggregate elastic parameters are calculated from the single crystal elastic constants via the Voigt–Reuss–Hill approximations. Mechanical stability, sound velocities, ductility/brittleness, elastic anisotropy, Debye temperature and pressure dependence of the elastic constants of the title compounds are also assessed. Since DFT with the common LDA and GGA underestimates the band gap, we use a new developed functional able to accurately describe the electronic structure of semiconductors, namely the Tran–Blaha-modified Becke–Johnson potential. The three investigated compounds demonstrate semiconducting behavior with indirect band gap(Γ–X) ranging from about 1.41 to 1.90 eV. The charge-carrier effective masses are evaluated at the topmost valence band and at the bottommost conduction band. The evolution of the value and nature of the energy band gap under pressure effect is also investigated. Optical functions, including the dielectric function , the refractive index , the extinction coefficient , the reflectivity , the linear absorption spectrum and the electron energy-loss are calculated for the energy range 0-20eV. The origins of the peaks and structures in the optical spectra are determined in terms of the calculated energy band structures.

Citation

Djamel ALLALI , Foudil SAHNOUNE , Abdelmadjid BOUHEMADOU, Fares ZERARGA, ,(2018), Structural, Elastic, Electronic and Optical PropertiesOf the LiZnX (X = P, As and Sb) filled-tetrahedral compounds: An ab initio FP-LAPW study,5thINTERNATIONAL CONFERENCE ON COMPUTATIONAL AND EXPERIMENTAL SCIENCE AND ENGINEERING (ICCESEN-2018) 10-14October 2018,,ANTALYA-TURKEY

The structural, electronic and optical properties of the LiZnP, LiZnAs and LiZnSb filled-tetrahedral compounds were explored using the full-potential (Linearized) augmented plane-wave plus local orbitals method (FP-(L)APW+lo)). Calculated structural parameters, including the lattice constant (a), bulk modulus (B) and its pressure derivative (B'), for the considered compounds using both the local density (LDA) and generalized gradient approximations (GGA) are consistent with the available data in the scientific literature. As the density functional theory with the common LDA and GGA underestimates the band gap, we have used a newly developed functional that is able to accurately describe the electronic structure of semiconductors, namely the Tran–Blaha-modified Becke–Johnson potential. The three investigated compounds demonstrate semiconducting behavior with indirect band gap (Γ–X) ranging from about 1.41 to 1.90 eV. The charge-carrier effective masses were evaluated at the topmost valence band and at the bottommost conduction band. The evolution of the value and nature of the energy band gap under pressure effect was also investigated. Optical functions of the tile compounds, including the dielectric function , refractive index , extinction coefficient , reflectivity , absorption coefficient and electron energy-loss function ,were calculated for the energy range 0-20eV. The origins of the peaks and structures in the optical spectra were determined in terms of the calculated energy band structures.

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Djamel ALLALI , Foudil SAHNOUNE , abdelmadjid Bouhemadou, Fares Zerarga, mohamed amine Ghebouli, abdelhak Bedjaoui, Monir Reffas, ,(2018), Electronic and optical properties of the LiZnX (X = P, As and Sb) filled-tetrahedral compounds,International Conference on Materials Science 2018 (ICMS2018),Setif , Algeria

The structural, elastic and thermodynamic properties of the LiZnN, LiZnAs and LiZnSb filled-tetrahedral compounds were investigated through ab initio full-potential linearized augmented plane wave calculations. Calculated structural parameters, including the lattice constant (a), bulk modulus (B) and its pressure derivative (B'), for the considered compounds using both the local density (LDA) and generalized gradient approximations (GGA) are in good agreement with the available experimental and theoretical data. The single crystal elastic constants were numerically estimated using total energy-strain approach with two different sets of distortions. The polycrystalline aggregate elastic parameters were calculated from the single crystal elastic constants via the Voigt–Reuss–Hill approximations. Mechanical stability, sound velocities, ductility/brittleness, elastic anisotropy, Debye temperature and pressure dependence of the elastic constants of the title compounds were also assessed. Temperature dependences of the lattice parameter, bulk modulus, volume thermal expansion coefficient, isochoric and isobaric heat capacity and Debye temperature in a wide temperature interval at some different fixed pressures were predicted through the quasi-harmonic Debye model.

Citation

Djamel ALLALI , Foudil SAHNOUNE , Abdelmadjid BOUHEMADOU, Fares ZERARGA, ,(2018), Structural, Elastic and Thermodynamic Properties Of the LiZnX (X = N, As and Sb) filled-tetrahedral compounds: An ab initio FP-LAPW study,4th International Conference on Advances in Mechanical Engineering ISTANBUL 2018 (ICAME2018)” scheduled from 19 – 21 December 2018,Istanbul, TURKEY

The structural, elastic and thermodynamic properties of the LiCdAs, LiCdSb and LiCdBi filled-tetrahedral compounds were investigated through ab initio full-potential linearized augmented plane wave calculations. Calculated structural parameters, including the lattice constant (a), bulk modulus (B) and its pressure derivative (B'), for the considered compounds using both the local density (LDA) and generalized gradient approximations (GGA) are in good agreement with the available experimental and theoretical data. The single crystal elastic constants were numerically estimated using total energy-strain approach with two different sets of distortions. The polycrystalline aggregate elastic parameters were calculated from the single crystal elastic constants via the Voigt–Reuss–Hill approximations. Mechanical stability, sound velocities, ductility/brittleness, elastic anisotropy, Debye temperature and pressure dependence of the elastic constants of the title compounds were also assessed. Temperature dependences of the lattice parameter, bulk modulus, volume thermal expansion coefficient, isochoric and isobaric heat capacity and Debye temperature in a wide temperature interval at some different fixed pressures were predicted through the quasi-harmonic Debye model.

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Djamel ALLALI , Fares ZERARGA, Abdelmadjid BOUHEMADOU, ,(2018), Structural, elastic and thermodynamic properties of the LiCdX (X = As, Sb and Bi) filled-tetrahedral compounds: An ab initio FP-LAPW study,5thINTERNATIONAL CONFERENCE ON COMPUTATIONAL AND EXPERIMENTAL SCIENCE AND ENGINEERING (ICCESEN-2018) 10-14October 2018,,ANTALYA-TURKEY

The structural and elastic properties of the GeMg2O4, GeZn2O4 and GeCd2O4 cubic spinels have been investigated through ab-initio full-potential linearized augmented plane wave calculations. The structural parameters calculated using both the local density LDA and generalized gradient approximations GGA to the exchange-correlation potential are in good agreement with the available experimental and theoretical data. The single crystal elastic constants are numerically estimated using total energy-strain approach with two different sets of distortions. The polycrystalline aggregate elastic parameters were calculated from the single crystal elastic constants via the Voigt–Reuss–Hill approximations. Mechanical stability, sound velocities, ductility/brittleness, elastic anisotropy, Debye temperature and pressure dependence of the elastic constants of the title compounds are also assessed.

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Djamel ALLALI , Fares ZERARGA, Abdelmadjid BOUHEMADOU, ,(2018), Structural, elastic and thermodynamic properties of the GeB2O4 (B = Mg, Zn and Cd) cubic spinels: An ab initio FP-LAPW study.,5thINTERNATIONAL CONFERENCE ON COMPUTATIONAL AND EXPERIMENTAL SCIENCE AND ENGINEERING (ICCESEN-2018) 10-14October 2018,,ANTALYA-TURKEY

The structural, elastic and thermodynamic properties of the LiCdN, LiCdP, LiCdAs and LiCdSb filled-tetrahedral compounds were investigated through ab initio full-potential linearized augmented plane wave calculations. Calculated structural parameters, including the lattice constant (a), bulk modulus (B) and its pressure derivative (B'), for the considered compounds using both the local density (LDA) and generalized gradient approximations (GGA) are in good agreement with the available experimental and theoretical data. The single crystal elastic constants were numerically estimated using total energy-strain approach with two different sets of distortions. The polycrystalline aggregate elastic parameters were calculated from the single crystal elastic constants via the Voigt–Reuss–Hill approximations. Mechanical stability, sound velocities, ductility/brittleness, elastic anisotropy, Debye temperature and pressure dependence of the elastic constants of the title compounds were also assessed. Temperature dependences of the lattice parameter, bulk modulus, volume thermal expansion coefficient, isochoric and isobaric heat capacity and Debye temperature in a wide temperature interval at some different fixed pressures were predicted through the quasi-harmonic Debye model.

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Djamel ALLALI , Fares Zerarga, abdelmadjid Bouhemadou, AbdelhakBedjaoui, ,(2018), Elastic and thermodynamic properties of the LiCdX(X=N,P,As and Sb) filled-tetrahedral compounds : An ab-initio FP-LAPW study’’,,(Communication par Affiche). at the International Conference on Materials Science (ICMS2018), to beheldfrom 12th to 14th September, 2018,SETIF , ALGERIA.

The structural, elastic and electronic properties under pressure effect of the AIX (X=N, P and As) compounds in the ZnS-type (B3) and NaCl-type (B1) structures were investigated using first- principles pseudopotential plane wave method based on density functional theory (DFT) with the LDA and GGA as implemented in the CASTEP code. Our results confirm that these compounds crystallize in the zinc-blende phase (B3) at ambient conditions and undergo a structural phase transition from B3 phase to B1 phase under the effect of hydrostatic pressure. Computed single elastic constants increase linearly with increasing pressure and verify the generalized stability criteria. It is found that the hardness of the AIX (X= N, P and As) compounds decreases with increasing atomic number Z of the X element. Calculated electronic properties reveal that the three considered compounds in the B3 phase and the AIN compound in the B1 phase are indirect band gap semiconductors, while the AIP and AIAs compounds in the B1 phase are metals. The nature of the fundamental band gap remainders unchanged under pressure effect. Calculated density of states reveals that these compounds possess a mixture of ionic and covalent bonding.

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Djamel ALLALI , Abdelhak Bedjaoui, Abdelmadjid Bouhemadou, Fares Zerarga, S. Bensalem. ‘, ,(2018), Structural, Elastic and Electronic properties of the AlX (X = N, P and As) in the B3 and B1 phases,the International Conference on Materials Science (ICMS2018),Setif , Algeria