SABER Saad essaoud

لعباشي العمري , جودي عبد السلام, مهيريس نصرالدين

تطبيق نظرية دالية الكثافة في دراسة الخواص البنيوية، الالكترونية، المغناطيسية والضوئية لبعض مركبات البيروفيسكايت

بن مهني رؤى

Pressure and temperature influences on thermal and thermoelectric properties of some materials used in thermoelectric generators

صغيور محمد , بن عربية عبد الكريم

Ab initio exploration of pressure effect on structural parameters, electronic structure and magnetic properties of some perovskite compounds

Ben Amara Ilyes , Bekhedda Belalia

Estimating the Influence of Temperature on the Properties of Some Semiconductors Using the Debye and Boltzmann Models

سيدعلى فرحاتي

استقصاء السلوك شبه الموصل في بعض المواد المغناطيسية

Refeida MEFTAH

Theoretical investigation of structural, electronic and magnetic properties of Heusler alloys

KETFI Mohammed Elamin

Contribution to the study of the physical properties of chalcostibites and emplectites materials: Photovoltaic applications

آمنة قريشي

AgMgF3 وKAgF3 دراسة نظرية للخواص البلورية ، الالكترونية والضوئية للمركبين

لقليطي مروة

CsVO3 دراسة الخواص الكهرو حرارية والترموديناميكية للمركب

حريزي أمينة

Etude théorique des propriétés structurales, électroniques et magnétiques du composé Co2AlB2

This study employs first-principles density functional theory (DFT) to comprehensively investigate the structural, electronic, magnetic, optical, and thermoelectric properties of the FeMnCrGe quaternary Heusler alloy, an unexplored material. Using the WIEN2k simulation package, the crystal structure was optimized with the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method and the Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA). The optimized lattice constant of 5.8076 Å and a negative formation energy confirm the alloy’s thermodynamic stability. Elastic analysis reveals a brittle nature, with a high Young’s modulus and a Poisson ratio of 0.229, indicating the predominance of covalent bonding. The computed electronic structure verifies the alloy's half-metallic nature, with the spin-up state acting as a metal and the spin-down state as a semiconductor. This behavior is accompanied by an indirect band gap (Γ-X) of 0.974 eV, determined via the mBJ approximation. The total magnetic moment of 1.00 μB demonstrates the compound's compliance with the Slater-Pauling rule, affirming its stable ferromagnetic nature. Characterized by a high refractive index across the visible wavelengths, as well as strong ultraviolet absorption, this material is highly suitable for photovoltaic use. The alloy’s thermoelectric performance, assessed with the BoltzTraP code, is marked by a Seebeck coefficient of 124.1 μV K−1 and a figure of merit of 0.42 at 500 K, suggesting its effectiveness for energy conversion. These insights highlight FeMnCrGe's potential as a multifunctional material for spintronics and photovoltaics and suggest experimental validation for practical implementation.

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SABER Saad Essaoud , Hasan A. Masri, Mohammed S. Abu-Jafar, Noorhan F. AlShaikh Mohammad, , (2025-01-29), Extensive DFT study of FeMnCrGe quaternary Heusler alloy: structural, elastic, magnetic, optical and thermoelectric properties, Optical and Quantum Electronics, Vol:57, Issue:2, pages:139, Springer

Based on the density functional theory, the double half-Heusler alloys LuXCo2Bi2 (X = V, Nb, and Ta) were studied to predict their structural, thermodynamic, thermoelectric, and optical characteristics. All the considered alloys are thermodynamically stable and have semiconductor behavior with indirect band gaps of 0.62, 0.75, and 0.8 eV for LuVCo2Bi2, LuNbCo2Bi2, and LuTaCo2Bi2, respectively. The investigated compounds exhibit semiconducting behavior with energy gaps below 0.8 eV. The impact of heat and pressure on thermodynamic coefficients was evaluated, and the influence of charge carriers on the temperature-dependent properties was studied using the semi-classical Boltzmann model. The studied compounds were characterized by their low lattice thermal conductivity at room temperature and low thermal expansion coefficient. These alloys exhibit substantial absorption coefficients in the ultraviolet (UV) light region, high optical conductivity, and high reflectivity in the visible light region, making them highly appealing materials for applications in the energy and electronics sectors.

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SABER Saad Essaoud , MOHAMMED ELAMIN KETFI , Said Al Azar, Anas Y. Al-Reyahi, Ahmad A. Mousa, Nabil Al Aqtash, , (2025-01-07), Insight into physical properties of lutetium-based double half-Heusler alloys LuXCo2Bi2 (X = V, Nb and Ta), Journal of Rare Earths, Vol:43, Issue:1, pages:199-208, Elsevier

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

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

Lead-free halide double perovskite materials have recently attracted considerable interest from the scientific community due to their vast potential in optoelectronic applications without toxicity issues. In this research, the physical properties of double halide perovskites (DP) were theoretically analyzed using the full-potential linearized augmented plane wave (FPLAPW) approach within the framework of density functional theory (DFT). The generalized gradient approximation (GGA) was utilized to compute key physical properties. The stability of both perovskites was confirmed through volume optimization curves and corresponding formation energies. Furthermore, electronic properties were assessed, and the band gap was determined. The results reveal semiconducting behavior with a direct band gap of 2.6 eV, suggesting its potential for solar cell applications.

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Imane Layaida , FADILA Mezrag , SABER Saad Essaoud , NADIR Bouarissa , ,(2024-11-09), DFT analysis of the physical characteristics of lead-free halide double perovskites.,The 1st International Conference of Materials Engineering and Renewable Energy (I C M E R E 2024),University May 8, 1945 Guelma Algeria Faculty of Science and Technology Department of Mechanical Engineering

The present work involves a computational investigation of the elastic, thermal, and thermoelectric characteristics of Ba2MnReO6, Ba2NiReO6, and Sr2MnReO6 from the Double Perovskite family. The study verified the mechanical stability of the three compounds and investigated Young’s modulus, Poisson, bulk, and shear modulus in various stress orientations. We were also able to compute longitudinal, transverse, and average sound velocities (Vl, Vt, and Vm, in m/s), and the findings revealed that Sr2MnReO6 had a greater longitudinal velocity than the other two compounds. Thermodynamic characteristics revealed that Ba2MnReO6, Ba2NiReO6, and Sr2MnReO6exhibit low lattice thermal conductivity (Kl) at medium temperatures, strong heat absorption, and a moderate coefficient of thermal expansion.The analysis of the electron and hole charge carriers’ transport characteristics revealed that, when doped with an electron concentration close to 1020 cm−3, the two materials, Ba2MnReO6 and Sr2MnReO6, may have an excellent figure of merit surpassing 0.6 at temperatures over 600 K.

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SABER Saad Essaoud , MOHAMMED ELAMIN KETFI , Said M. Al Azar, Anas Y. Al-Reyahi, , (2024-10-18), Computational prediction of Thermo-Elastic and charge carriers transport properties of Ba2MnReO6, Ba2NiReO6, and Sr2MnReO6 double Perovskite compounds, Chemical Physics Letters, Vol:857, Issue:, pages:141694, Elsevier

The potential of halide perovskites has transformed the field of optoelectronics and energy conversion. In this study, the physical properties of double halide perovskites (DP) were investigated theoretically using the full-potential linearized augmented plane wave (FPLAPW) method within the framework of DFT. The generalized gradient approximation (GGA) was employed to calculate relevant physical characteristics. Stability for both perovskites was verified through volume optimization curves and corresponding formation energies. Additionally, electronic properties were examined, and band-gap were calculated. The findings indicate a semiconducting behavior with a direct band-gap of 2.6 eV, highlighting its potential for solar cell applications.

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Imane Layaida , FADILA Mezrag , SABER Saad Essaoud , NADIR Bouarissa , ,(2024-10-11), Study of the structural and electronic properties of double perovskites for energy applications,JSI'2024 - International Conference on Engineering Sciences 11ème Édition des Journées des Sciences de L’Ingénieur,University of Sfax, National School of Engineers of Sfax (ENIS), Tunisia.

The structural, elastic, thermodynamic, electronic, and thermoelectric characteristics of K2BaCdSb2 were investigated utilizing ab initio methods. The structural, elastic, and thermodynamic properties were calculated using the pseudopotential plane wave approach with the GGA-PBEsol exchange-correlation functional. The computed equilibrium structural characteristics closely match the available data. The anticipated elastic constants reveal that K2BaCdSb2 is mechanically stable, brittle, and exhibits significant elastic anisotropy. The full potential linearized augmented plane wave approach with the Tran-Blaha modified Becke-Johnson potential was used to determine the electronic structure of K2BaCdSb2.It is found that K2BaCdSb2 is a semiconductor with a Γ-Γ type direct bandgap of 0.85 eV. Bonding analysis shows the bond between Cd and Sb atoms within the polyanion is of covalent nature and that between the K/Ba atom and the polyanion is of ionic character. The thermoelectric characteristics of K2BaCdSb2 were analyzed at a temperature of 500 K for of charge-carrier concentrations from 1 × 1018 to 3 × 1020 cm−3.When the concentration of holes is 1.0 × 1020 cm−3, The power factor reaches a value of 17 × 1010 W m−1 K−2.s−1 for a hole concentration of 1.0 × 1020 cm−3. For the p-doped K2BaCdSb2 with a concentration of 1.0 × 1018cm−3, the electronic figure of merit is 0.95.

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SABER Saad Essaoud , Hadjer Nasrallah, Nacir Guechi, Abdelmadjid Bouhemadou, Saad Bin-Omran, , (2024-09-25), Study of the fundamental physical characteristics of the Zintl phase K2BaCdSb2, Computational Condensed Matter, Vol:41, Issue:, pages:e00966-e00979, Elsevier

Several exchange–correlation potentials within the framework of Density Functional Theory (DFT) were used to study the structural, electronic, magnetic, optical, and thermoelectric properties of cubic perovskites CsEuX3 (X=Cl, Br, and I). The exchange–correlation potentials used in this study include GGA, mBJ, and GGA+U, both with and without spin–orbit coupling (SOC). The stability of all compounds was confirmed by the obtained values of the cohesive energy, formation energy, and tolerance factor. When GGA+U with SOC is used, all compounds show direct bandgap with no effect of the spin state on the bandgap value. The bandgap varies differently for spin-up and spin-down states under pressure. Europium ions control the magnetic properties. Optical investigations indicate that CsEuBr3 and CsEuI3 exhibit identical characteristics, whereas CsEuCl3 has a similar trend but shifted to higher energy. Absorption mostly takes place in the UV region, whereas there is about 20 % reflectance in the infrared (IR) and visible regions. All compounds have low energy loss and excellent transparency. Our investigation indicates that the present compounds are good thermoelectric materials with a high figure of merit. For example, CsEuCl3 demonstrates a figure of merit (ZT) ranging from 0.82 to 0.86 for spin-up and around 1 for spin-down over the temperature range 50–800 K. Such encouraging results indicate that all compounds are potential candidates for optical applications and thermoelectric devices.

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SABER Saad Essaoud , MOHAMMED ELAMIN KETFI , ADMIN Admin , Anas Y. Al-Reyahi, Said M. Al Azar, Mufeed Maghrabi, , (2024-09-19), An ab initio study to investigate the physical properties of CsEuX3 (X=Cl, Br, and I) using different Exchange-Correlation potentials, Results in Physics, Vol:65, Issue:, pages:107980-107991, 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

CsZnX3 (X = F, Cl, Br, I) cubic perovskite compounds were investigated using Wien2K with PBE and mBJ energy exchange potentials to determine their structural, electronic, optical, thermoelectric, and thermodynamic properties. The results of Phonon vibrational frequency, formation energy, and cohesive energy show that all compounds are stable. The electronic properties revealed that CsZnF3 has the highest indirect bandgap as an insulator, followed by CsZnCl3 and CsZnBr3, and CsZnI3 has the lowest indirect bandgap. CsZnX3 (X = Cl, Br, I) are classified as p-type semiconductors based on their electronic structure and the positive values of the Seebeck coefficient. High transparency was shown by low visible and infrared absorption. The investigated compounds exhibit high power factor and high figure of merit (ZT), which exceeds 0.7 over the temperature range 300–800 K. As the material’s temperature rises, its lattice heat conductivity decreases in accordance with thermodynamics. However, when the temperature exceeds the Debye temperature, the volume heat capacity matches the Dulong-Petit limits and the experimental results.

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SABER Saad Essaoud , MOHAMMED ELAMIN KETFI , Akram Aqili, Said M. Al Azar, Anas Y. Al-Reyahi, Mufeed Maghrabi, Nabil Al Aqtash, Ahmad Mufleh, , (2024-06-22), Investigating the physical characteristics of inorganic cubic perovskite CsZnX3 (X = F, Cl, Br, and I): An extensive ab initio study towards potential applications in photovoltaic perovskite devices, Computational and Theoretical Chemistry, Vol:1238, Issue:, pages:114721-114731, Elsevier

This study evaluated the characteristics of the compounds Ba2MnReO6, Ba2NiReO6, and Sr2MnReO6 from the Double Perovskites family using density function theory. The acquired data suggested that these three compounds are thermodynamically stable under pressures of up to 15 GPa, with bulk modulus surpassing 160 GPa. Furthermore, these compounds exhibited magnetic properties, with total magnetic moments of 3.95, 1.94, and 3.3μB for Ba2MnReO6, Ba2NiReO6, and Sr2MnReO6, respectively. In terms of electrical behavior, the three compounds were found to have an energy gap of 2.0, 3.0, and 1.2 eV in the spin-up (majority) channel of Ba2MnReO6, Ba2NiReO6, and Sr2MnReO6, respectively, whereas they exhibited a metallic spin in the spin-down state. Several optical properties of the three compounds were also verified, such as absorption coefficient, refraction and reflection coefficients, optical conductivity, as well as the loss energy.

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SABER Saad Essaoud , MOHAMMED ELAMIN KETFI , Said Al Azar, Anas Y. Al-Reyahi, Ahmad Mufleh, , (2024-05-25), Computational study of structural parameters, magnetic properties, half metallicity, and linear optical characteristics of transition-metal oxide double perovskites: Ba2MnReO6, Ba2NiReO6, and Sr2MnReO6, Indian Journal of Physics, Vol:99, Issue:1, pages:117–124, Springer Nature

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

The cubic perovskites CsGeBr3-nIn (n = 0, 1, 2, 3) were investigated using the density functional theory (DFT) for their structural, electronic, and optical properties. The present DFT calculations are carried out using three models for exchange-correlation potential, namely PBE, mBJ, and YS-PBE0. The bandgap decreases in the above sequence of compounds except CsGeBrI2, which reveals the smallest bandgap. The mBJ approximation has a larger bandgap than the PBE and smaller than the YS-PBE0. Results of calculations within the YS-PBE0 approach for CsGeBr3 and CsGeI3 agree well with QSGW + SO results. The CsGeBr3-nIn compounds are direct bandgap semiconductors and CBM and VBM are positioned at the R point and determined mainly by Ge s-states and Br(I) p-states, respectively. Analysis of optical properties shows that the DFT calculations within the PBE model consistently produce the highest static dielectric function values, while the YS-PBE0 method gives the smallest values. The curves of optical coefficients shift toward lower energies when decreasing the Br atoms in CsGeBr3-nIn. The studied compounds are semitransparent in the infrared and visible regions and show promising potential for photovoltaic applications, including solar cells

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SABER Saad Essaoud , SABER Saad Essaoud , Anas Y. Al-Reyahi and Ahmad Mufleh and Said M. {Al Azar} and Mufeed Maghrabi and Nabil {Al Aqtash}, ; Khadidja Berarma ; Adel Shaheen ; Mohammed Elamin Ketfi ; Ahmad A. Mousa, , (2023-12-30), Exploring the physical properties of cubic CsGeBr3-nIn (n= 0, 1, 2, 3) compounds: Ab initio calculations of perovskites prospective for the application in solar cells, Solid State Sciences, Vol:148, Issue:1, pages:107435, Elsevier

The cubic perovskites CsGeBr3-nIn (n = 0, 1, 2, 3) were investigated using the density functional theory (DFT) for their structural, electronic, and optical properties. The present DFT calculations are carried out using three models for exchange-correlation potential, namely PBE, mBJ, and YS-PBE0. The bandgap decreases in the above sequence of compounds except CsGeBrI2, which reveals the smallest bandgap. The mBJ approximation has a larger bandgap than the PBE and smaller than the YS-PBE0. Results of calculations within the YS-PBE0 approach for CsGeBr3 and CsGeI3 agree well with QSGW + SO results. The CsGeBr3-nIn compounds are direct bandgap semiconductors and CBM and VBM are positioned at the R point and determined mainly by Ge s-states and Br(I) p-states, respectively. Analysis of optical properties shows that the DFT calculations within the PBE model consistently produce the highest static dielectric function values, while the YS-PBE0 method gives the smallest values. The curves of optical coefficients shift toward lower energies when decreasing the Br atoms in CsGeBr3-nIn. The studied compounds are semitransparent in the infrared and visible regions and show promising potential for photovoltaic applications, including solar cells

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SABER Saad Essaoud , SABER Saad Essaoud , Anas Y. Al-Reyahi and Ahmad Mufleh and Said M. {Al Azar} and Mufeed Maghrabi and Nabil {Al Aqtash}, ; Khadidja Berarma ; Adel Shaheen ; Mohammed Elamin Ketfi ; Ahmad A. Mousa, , (2023-12-30), Exploring the physical properties of cubic CsGeBr3-nIn (n= 0, 1, 2, 3) compounds: Ab initio calculations of perovskites prospective for the application in solar cells, Solid State Sciences, Vol:148, Issue:1, pages:107435, Elsevier

A full-potential linear augmented plane wave (FP-LAPW) has been used to study the structural, electronic, and optical properties of double half-Heusler alloys X2FeY′Sb2 with X≡Zr, Hf and Y′≡Pd, Ni. Electronic band structures and densities of states calculations of the four studied double half-Heusler alloys indicate that they are semiconductors with an indirect gap. The optical spectra of dielectric constants, refractive indices, reflectivity, and light absorption are also discussed. In the energy range of 8–14 eV, the calculated optical properties and mainly the absorption spectrum show very high UV absorption. Additionally, DFT calculations were combined with Boltzmann transport theory to estimate the thermoelectric properties, such as the thermal and electrical conductivity, Seebeck coefficient, and figure of merit (ZT), versus the change of temperature and chemical potential. These alloys possess a suitable band gap for diverse optoelectronic applications, encompassing photovoltaics, UV sensors, and solar cells.

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Khedidja BERARMA , SABER Saad Essaoud , Said Al Azar;,Anas Y. Al-Reyahi,Ahmad A. Mousa; Ahmad Mufleh, , (2023-12-11), Computational characterization of structural, optoelectronic and thermoelectric properties of some double half-Heusler alloys X2FeY′Sb2 (X: Hf, Zr ;Y′: Ni, Pd), Phase Transitions, Vol:96, Issue:11, pages:1-16, Taylor & Francis

We report an analysis of the structural, electronic, mechanical, and thermoelectric properties of oxide double perovskite structures, specifically the compounds Ba2MgReO6 and Ba2YMoO6. Our study employs first-principles density functional theory (DFT) as the investigative methodology. The electronic attributes of the examined compounds are explained by investigating their energy bands, as well as the total and partial density of states. The computational evaluation of the electronic band structure reveals that both compounds exhibit an indirect band gap semiconductor behavior in the spin-down channel, while demonstrating metallic properties in the spin-up channel. The magnetic attributes indicate a ferromagnetic nature, thus categorizing some double perovskite compounds as materials displaying half-metallic ferromagnetism (HM-FM) in addition to some other properties such as metallic and semiconductor in paramagnetic or antiferromagnetic states. The outcomes derived from the analysis of elastic constants confirm the mechanical robustness of the studied double perovskite compounds. Notably, the computed data for bulk modulus (B), shear modulus (G), and Young's modulus (E) for Ba2MgReO6 surpass those of Ba2YMoO6. The calculated ratio of Bulk to shear modulus (B/G) indicates that both compounds possess ductile characteristics, rendering them suitable for device fabrication. Furthermore, both compounds display outstanding electronic and elastic properties, positioning them as promising contenders for integration within mechanical and spintronic devices. Finally, we investigate into the thermoelectric potential by evaluating parameters such as the Seebeck coefficient, electrical conductivity, thermal conductivity, figure of merit, and power factor. This assessment is conducted using the semiclassical Boltzmann theory and the constant relaxation time approximation, implemented through the BoltzTraP code. The results indicate that the investigated double perovskite oxides hold promise for utilization in thermoelectric applications.

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SABER Saad Essaoud , MOHAMMED ELAMIN KETFI , Said M Al Azar, Anas Y Al-Reyahi, Ahmad A Mousa, Nabil Al-Aqtash, , (2023-12-07), Mechanical, magneto-electronic and thermoelectric properties of Ba2MgReO6 and Ba2YMoO6 based cubic double perovskites: an ab initio study, Physica Scripta, Vol:99, Issue:1, pages:015908-015923, IOPscience

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 single-crystal 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. Keywords: Double half Heusler; Quantum espresso; Spin orbit coupling effect; Thermoelectricity; Elastic constants; Thermal properties

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SABER Saad Essaoud , Abdelmadjid Bouhemadou, Missoum Radjai, Mohammed Elamin Ketfi, Djamel Allali, Saad Bin-Omran, S. Maabed,, , (2023-11-16), 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:1, pages:111733, Elsevier

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

Physical properties of Be-based fluoroperovskite compounds XBeF3 (X = K, Rb): a first-principles study}, journal = {Journal of Physics: Condensed Matter}, abstract = {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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SABER Saad Essaoud , Sarah Chaba Mouna and Missoum Radjai and Md. Atikur Rahman and Abdelmadjid Bouhemadou and Abdullah and Djamel Houatis and Djamel Allali and and Hatem Allaf, , (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:5, pages:055701, IOPscience

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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SABER Saad Essaoud , Hatem Allaf, Missoum Radjai, Djamel Allali, Abdelmadjid Bouhemadou, Saad Bin-Omran, Rabah Khenata, Yarub Al-Douri, , (2023-10-21), 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:1, pages:e00850, Elsevier

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.

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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) 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 , , (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:1, Issue:, pages:-, 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 this work, we performed first-principles calculations based on density functional theory and the semi-classical Boltzmann method to investigate the structural, optoelectronic, magnetic, thermodynamic and thermoelectric properties of PdAlO2, PdCrO2 and PdRhO2 in the Tetragonal phase. Our calculations have revealed that these three compounds have indirect band gaps in the range of 2.14 to 2.68 eV. The thermodynamic properties are investigated using the quasi-harmonic model, where heat capacities at constant pressure and volume, entropy, Debye temperature, and thermal expansion coefficient are analyzed and discussed under both pressure and temperature effects. As a result of this study, PdAlO2, PdCrO2, and PdRhO2 are promising materials for optoelectronic devices, especially photovoltaic materials in solar cells. In doing so, we computed for each compound the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and figure of merit in the temperature range from 300 to 500 K. The relaxation time and lattice thermal conductivity are calculated as well. Our results reveal that low thermal conductivity and a high Seebeck coefficient can be achieved at the same time. In addition, they exhibit a higher Seebeck for PdAlO2 compared to PdBO2 (B = Cr and Rh) up to 1.6 mV/K for PdAlO2 at 300 K. Thereby improving their thermoelectric performance which makes them attractive thermoelectric materials at high temperatures.

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SABER Saad Essaoud , , (2023-09-15), Insight into the spin-polarized structural, optoelectronic, magnetic, thermodynamic, and thermoelectric properties of PdBO2 (B = Al, Cr, and Rh) Delafossite semiconductor, Optical and Quantum Electronics, Vol:55, Issue:, pages:-, Springer

Structural, elastic, electronic, optical, and thermoelectric properties of cubic double perovskites X2AgBiBr6 (X = Li, Na, K, Rb, Cs) were investigated using the density functional theory (DFT) method. The DFT calculations were carried out with various exchange-correlation potentials, e.g. LDA, GGA-PBE, GGA-WC, and hybrid functionals (YS-PBE0). Structural and elastic properties of X2AgBiBr6 demonstrate that these compounds are ionically bonded, elastically stable, ductile, and anisotropic. Calculations show that the compounds are semiconductors with indirect bandgap at the (X- L) point, with bandgap values of 2.124, 2.222, 2.198, 2.209, and 1.902 eV for X2AgBiBr6 (X = Li, Na, K, Rb, and Cs), respectively. Due to their distinguishing optical characteristics and indirect wide bandgap, these compounds might be utilised as absorber layers in solar cells and other optoelectronic devices. Moreover, thermoelectric properties show that the Figure of Merit (ZT) has values of 0.713, 0.723, 0.721, 0.726, and 0.728 for X2AgBiBr6 (X = Li, Na, K, Rb, Cs). The Figure of Merit shows a plateau in the temperature range of 500–900 K, which corresponds to the highest value of ZT. All investigated compounds have holes as the majority of charge carriers. Thermoelectric properties of X2AgBiBr6 compounds reveal that these compounds can be employed in thermoelectric devices.

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SABER Saad Essaoud , , (2023-08-29), First-principles calculations to investigate structural, mechanical, electronic, optical, and thermoelectric properties of novel cubic double Perovskites X2AgBiBr6 (X=Li, Na, K, Rb, Cs) for optoelectronic devices, MOLECULAR SIMULATION, Vol:49, Issue:16, pages:1561-1572, Taylor & Francis

The density functional theory as a computational approach was used to explore the ferrimagnetic semiconducting behavior of Dy2CoMnO6 double perovskite compound in both spin-up and spin-down directions. Thermodynamic stability was confirmed in a wide pressure range set to 30 GPa. Both scalar and full relativistic calculations are used to estimate the spin–orbit effect. The topological distribution of the charge density and the net effective charge of each atom are studied based on the Quantum Theory of Atoms in Molecules (QTAIM) as implemented in Bader code, Besides this, the different QTAIM atomic basins descriptors such as electron density ${{\boldsymbol{\rho }}}_{{\boldsymbol{b}}},$ Laplacian of the electron density ${{\rm{\nabla }}}^{2}{{\boldsymbol{\rho }}}_{{\boldsymbol{b}}},$ potential electronic energy density ${{\boldsymbol{V}}}_{{\boldsymbol{b}}},$ kinetic electronic energy density ${{\boldsymbol{G}}}_{{\boldsymbol{b}}}\,$and density of the total electronic energy ${{\boldsymbol{H}}}_{{\boldsymbol{b}}}\,$at bond critical points (BCPs) are estimated using CRITIC2 software where the ionic type for Dy-O, Co-O, and Mn-O bonds are evaluated. Holes and electrons have different effective masses, their thermoelectric properties appear high figure of merit (ZT) exceeding 0.5 for temperatures greater than 500 K in the negative chemical potential region, suggesting that doping with holes might be more favorable for thermoelectric efficiency than doping with electrons.

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SABER Saad Essaoud , , (2023-06-20), DFT-based investigation of electronic-structure, magnetic and thermoelectric properties of Dy2CoMnO6 double perovskite, Physica Scripta, Vol:98, Issue:7, pages:075930, IOPscience

n this study, we employed the ab initio pseudopotential plane wave approach, utilizing the GGA-PBEsol 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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SABER Saad Essaoud , Sara Chaba Mouna ; Missoum Radjai ; Abdelmadjid Bouhemadou ; Djamel Houatis ; Djamel Allali , Saad Bin-Omran, , (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 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

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. Keywords: Double half Heusler; Electronic structure; Optical coefficients; Charge density distribution map

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SABER Saad Essaoud , A. Bouhemadou, Mohammed Elamin Ketfi, D. Allali, S. Bin-Omran, , (2023-03-17), 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

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

Born effective charges Z(i),β α *, dielectric tensors ε α,β and the dynamic stability for AgMgF3 and KMgF3 compounds were treated based on the harmonic and quasi-harmonic theory implemented in phonopy code. The band gap for both compounds, and the effective masses of electrons and holes are calculated at different pressures using the TB-mBJ (GGA) approximation within the framework of the density functional theory. Furthermore, absorption coefficient, refractive index, extinction coefficient, reflectivity, and optical conductivity, for both compounds, were calculated. On the other hand, we studied the nature of atomic bonds by the topological distribution of the charge density as well as computing the effective charge of each atom based on the Quantum Theory of Atoms in Molecules (QTAIM) as implemented in Bader code, therefore the ionic type for bonds was explored. The mechanical stability was verified the elastic behavior at the equilibrium ground-state for both compounds. Thermal properties such as heat capacity at constant volume, entropy, Debye temperature, and thermal expansion coefficient are treated depending on the quasi-harmonic model. They are examined under both pressure and temperature influences. The thermoelectric properties of the compound AgMgF3 showed a high figure of merit (ZT) reached 0.75 at a temperature of 300 K in the case if it was grafted with a concentration of 1021 cm−3 of n-type

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SABER Saad Essaoud , Said M Al Azar , Ahmad A Mousa , Riad S Masharfe, , (2023-02-14), Characterization of structural, dynamic, optoelectronic, thermodynamic, mechanical and thermoelectric properties of AMgF 3 (A=K or Ag) Fluoro-perovskites compounds, Physica Scripta, Vol:98, Issue:3, pages:035820, IOPscience

The cubic spinel structure of B2NO4 and Al2NO4 was investigated using ab-initio calculations for a better understanding of their electronic, bonding, and thermo-optical properties in spin-up and spin-down cases. The calculations were performed by integrating the generalized gradient approximation proposed by Perdew, Burke, and Ernzerhof (PBE-GGA) with the full potential linearized augmented plane wave (FP-LAPW). The elastic constants as well as the negative formation energies indicate that the studied compounds are stable. It was found that A2NO4 has a unit cell volume of about 30% larger than that of B2NO4. The band gap values for B2NO4 and Al2NO4 are 1.65 eV and 1.94 eV, respectively, for the spin-down case. Oxygen and nitrogen are the major elements in the determined total density of states (T-DOS). The bandgap results are consistent with the DOS results. This implies that the structures behave as half-metallic, going through a metallic phase during spin-up and a semiconductor phase during spin-down. The optical results for both compounds indicate distinct behaviors. Al2NO4 has a higher conductivity than B2NO4, but when all other studied optical properties were considered, B2NO4 is superior. A covalent bond that is close to an ionic bond was observed from the electron density. Additionally, the charge carriers for B2NO4 and Al2NO4 are holes for the spin-up case and electrons for the spin-down case.

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SABER Saad Essaoud , Anas Y. Al-Reyahi, Said Al Azar, Ahmad A. Mousa, Mufeed Maghrabi, Khadidja Berarma, Akram Aqili, Ahmad Mufleh, Heba I. Abu Radwan,, , (2023-01-13), Investigation of electronic, optical, and thermoelectric properties of half-metallic spinel X2NO4 (X=B, Al): First-principles calculations, Computational Condensed Matter, Vol:34, Issue:, pages:e00787, Elsevier

The structural, elastic, electronic, magnetic, and thermoelectric properties of MgEu2X4 (X = S and Se) spinel compounds are investigated computationally. Calculations are performed using the full-potential linearized augmented plane wave (FP-LAPW) method within the Perdew, Burke, and Ernzerhof generalized gradient approximation (PBE-GGA), GGA + U, and modified Becke–Johnson (mBJ-GGA) approximations. The band structure and density of states results from the three exchange-correlation approximation methods (mBJ, GGA + U, and PBE) show that these spinel compounds are fully spin-polarized. Also, they possess a half-metallic character in the spin-down channel with a direct bandgap (Γ–Γ) of about 3.44, 2.712, and 2.472 eV for MgEu2S4 and 2.89, 2.285, and 2.017 eV for MgEu2Se4, respectively. The formation of both compounds is energetically favorable based on the results of the total energy and cohesive energy calculations. Furthermore, the two compounds are chemically and mechanically stable, as concluded from cohesive energy and elastic calculations. The elastic calculations reveal that both spinel compounds are ductile materials. The ionic bonds are predominant. The quasi-harmonic model has also been used to investigate the influences of temperature and pressure on thermal characteristics. The thermoelectric behavior is studied using the BoltzTraP code. Both systems show good thermoelectric properties for the spin-down channel.

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SABER Saad Essaoud , Ahmad A. Mousa, Said M. Al Azar, Khadidja Berarma, Aymen Awad, Nada T. Mahmoud, Emad K. Jaradat, Mohammed S. Abu-Jafar, , (2022-07-27), Structural, Elastic, Electronic, Magnetic, and Thermoelectric Characteristics of MgEu2X4 (X = S, Se) Spinel Compounds: Ab‐Initio Calculations, physica status solidi (b), Vol:259, Issue:10, pages:2200191, Wiley

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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SABER Saad Essaoud , F. Zerarga, D. Allali, A. Bouhemadou, R. Khenata, B. Deghfel, R. Ahmed, Y. Al-Douri, S.S. Safaai, S. Bin-Omran, S.H. Naqib, , (2022-06-22), 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

The effect of constituent atoms on the physical properties of the MAX phase compounds M2AC and M2AB (M = Nb or Mo and A = Al or Ga) was studied theoretically. The obtained results showed that each MAX atom affects structural properties such as the equilibrium lattice constants, cohesive energy, and bulk modulus. Also, the thermodynamic stability was confirmed where all compounds have negative formation enthalpies. Voigt–Reuss–Hill approximations have been used to examine the mechanical stability of these compounds; various parameters for this purpose have been found such as Poisson’s ratio, shear, bulk modulus, and Young’s modulus. We applied the modified Becke–Johnson approximation (mBJ) to calculate the electronic band structure also total and partial density of states. Also, the study expanded towards the thermal properties, where the temperature dependency of the heat capacities at volume (Cv), the entropy (S), and the thermal expansion coefficient (α) are investigated. The semi-local Boltzmann transport theory has been used to investigate thermoelectric properties. By comparing the properties of the compounds according to their constituent atoms, we found that all the studied compounds have ceramic–metallic characters in particular Mo2AlC alloy, which have high cohesion energy and resist to pressure more than other compounds. In addition, it has electronic conductivity, high thermal conductivity, and a medium thermal absorption coefficient. We also recognized that each compound has a distinguishing feature: Mo2AlC has isotropic elastic characteristics, although Mo2GaC has high electrical (σ/τ) and thermal conductivity (κ/τ), whereas Nb2AlC has a low thermal expansion coefficient, and Nb2AlB has a greater heat capacity.

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SABER Saad Essaoud , Ahmed S. Jbara, , (2022-06-08), Electronic-structural, thermo-electric, and thermo-mechanical properties of M2AC and M2AB (M = Nb or Mo, A = Al or Ga) compounds, Indian Journal of Physics, Vol:97, Issue:, pages:105–114, Springer

A computational research study of the structural, electronic, and optical characteristics of double half-Heusler alloys Ta2FeNiSn2 and Nb2FeNiSn2 is presented by performing ab initio calculations. The density functional theory framework employs the full-potential linearized augmented plane wave method to solve Kohn–Sham equation as implemented in the Wien2k code. The exchange-correlation potential is processed by using the local density approximation and the generalized gradient approximation–Perdew, Burke, and Ernzerhof approximations to calculate the total energy and other physical properties. The obtained results showed that both alloys possess high cohesive energies, where Nb2FeNiSn2 (7.213 eV atom−1) is more consistent than Ta2FeNiSn2 (6.249 eV atom−1), these remarkable results support the structural stability for both alloys. Also, the thermodynamic stability of both compounds was confirmed through calculating the formation energy as the obtained results were close to the results obtained in as well as given the Open Quantum Materials Database. Electronic characteristics and chemical bonding are illustrated and discussed by computing the electron charge density, density of states, and band structure. Both alloys show semiconductor behavior with (∼0.5 eV) indirect energy bandgap. Also, we have calculated and analyzed the complex dielectric function, absorption coefficient, as well as, reflectivity spectra for both compounds. The semi local Boltzmann transport theory has been employed to treat temperature effect on thermoelectric properties of Ta2FeNiSn2 and Nb2FeNiSn2 compounds where the obtained results appears that both compounds have high coefficient at the normal condition, and they also have a good power factor at the Fermi level, which emphasizes that the thermoelectric efficiency of the two compounds is good and does not require doping. Also, depending on quasi-harmonic model was used for estimating the heat capacity, the lattice thermal conductivity, the thermal expansion and the Debye temperature under the pressure effects.

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SABER Saad Essaoud , Khadidja Berarma and Ahmad A Mousa and Said M Azar and Anas Y Al-Reyahi, , (2022-04-08), Opto-electronic, thermodynamic and charge carriers transport properties of Ta 2 FeNiSn 2 and Nb 2 FeNiSn 2 double half-Heusler alloys, Semiconductor Science and Technology, Vol:37, Issue:5, pages:055013, IOPscience

We have studied hydrostatic pressure dependence of the electronic, optical, thermodynamic and thermoelectric properties of CsVO3 via first principles calculations. In addition, temperature dependence of the thermoelectric and thermal parameters was investigated. The calculated equilibrium structural parameters are in excellent agreement with the available experimental counterparts. The calculated phonon-band dispersion curve confirms the dynamic stability of CsVO3 compound in its ground-state. Analysis of the energy band dispersion calculated within the TB-mBJ potential reveals that CsVO3 is a direct bandgap semiconductor with a fundamental bandgap of 3.14 eV. It is found that the bandgap increases with increasing pressure. Analysis of the DOS diagrams and charge density topology shows that the V-O bond is partially covalent and the Cs-O bond is predominantly ionic in nature. Frequency-dependent linear macroscopic optical coefficients, namely absorption coefficient, refractive index, extinction coefficient, reflectivity and optical conductivity, were deduced from the calculated real and imaginary parts of the complex dielectric function under hydrostatic pressure effect. The semi-classic Boltzmann transport theory was used to explore pressure and temperature dependencies of the thermoelectric properties. Pressure and temperature dependencies of the thermal parameters, viz., isochore and isobar heat capacities, lattice thermal conductivity, volume thermal expansion coefficient and Debye temperature, were explored through the quasi-harmonic Debye model.

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SABER Saad Essaoud , A. Bouhemadou, S. Maabed, S. Bin-Omran, R. Khenata, , (2022-03-31), Pressure dependence of the electronic, optical, thermoelectric, thermodynamic properties of CsVO3: first-principles study, Philosophical Magazine, Vol:102, Issue:15, pages:1522–1546, Taylor & Francis

Due to their useful physical properties, copper-based chalcogenides materials are recently promising for numerous emerging technological fields. In photovoltaics, discovering and designing suitable materials for solar cells is a primary technical challenge. The structural, electrical, optical, and thermoelectric properties for both CuYSe2 and CuYTe2 in the hexagonal phase, as well as CuYS2 in the orthorhombic phase have been investigated using a numerical Full Potential-Linearized Augmented Plane Wave (FP-LAPW) technique based on Density Functional Theory (DFT). To compute the structural properties, both, the local density approximation (LDA) and the generalized gradient approximation (PBE-GGA) were used as exchange-correlation potentials. On the other hand, the modified Becke-Johnson (mBJ) was used to compute the optoelectronic, properties with higher degree of precision. Our calculations revealed that these three compounds have indirect band gaps in the range of 0.6 eV–2.1 eV. Moreover, numerous thermoelectric qualities of the investigated compounds estimated as a function of chemical energy at different temperatures using the semi-local Boltzmann transport theory, whereby the findings exhibit a higher Seebeck coefficient for CuYS2 compared to CuYZ2(Z = Se and Te) up to 2.7 mV/K for CuYS2 at 300 K, with acceptable values of thermal and electronic conductivity. The quasi-harmonic model is used to examine thermodynamic properties such as heat capacity at constant pressure and volume, entropy, Debye temperature, and thermal expansion coefficient under both pressure and temperature influences. As a result of this study, CuYS2, CuYSe2 and CuYTe2 are promising materials for optoelectronic devices, especially as photovoltaic materials in solar cells.

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Hamza BENNACER , MOHAMMED ELAMIN KETFI , SABER Saad Essaoud , , (2021-12-10), Computational evaluation of optoelectronic, thermodynamic and electron transport properties of CuYZ2 (Z= S, Se and Te) chalcogenides semiconductors, Materials Chemistry and Physics – Elsevier., Vol:277, Issue:125553, pages:15, Elsevier

A theoretical investigation of the electronic structure and the magnetic and thermoelectric (TE) properties of KCrS, KCrSe, and KCrTe half-Heusler alloys is studied. The most stable structural−magnetic configuration is identified, taking into consideration three types of possible atomic arrangements. The results indicate that KCrZ (Z = S, Se, Te) alloys are completely spin-polarized half-metallic ferromagnets in their ground state. Band structure calculations demonstrate that all compounds exhibit large bandgaps in the localized minority spin channel with a significant magnetic moment and high spin polarization (100%). The temperature dependence of the TE properties, such as the Seebeck coefficient and the electrical and thermal conductivity coefficients, is discussed and investigated using the semi-local Boltzmann transport theory in the temperature range 250–1000 K. The quasiharmonic model is implemented to investigate and analyze the thermal parameters. In particular, thermal expansion coefficient, thermal conductivity, Debye temperature, specific heat capacity at constant volume, and entropy of the three novel half-Heusler alloys are calculated and interpreted.

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SABER Saad Essaoud , Telfah, Ahmad and Baaziz, Hakim and Charifi, Zoulikha and Alsaad, Ahmad Mohammad and A. Ahmad, Mais Jamil and Hergenröder, Roland and Sabirianov, Renat, , (2021-06-24), DFT Investigation of Physical Properties of KCrZ (Z=S, Se, Te) Half‐Heusler alloys., physica status solidi (b), Vol:258, Issue:10, pages:2100039, Wiley

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SABER Saad Essaoud , ,(2021-04-21), PRESSURE EFFECT ON THE MAGNETIC, ELECTRONIC AND ELASTIC STABILITY OF SOME MATERIALS USED IN THERMO-ELECTRIC GENERATORS,the first International Conference on Sustainable Energy and Advanced Materials IC-SEAM’21,Ouargla, ALGERIA

Electronic, magnetic, dynamic, elastic, thermodynamic, and thermoelectric properties for Co2-based full Heusler alloys are investigated theoretically. The full potential–linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT) incorporated on WIEN2k code is employed in our calculation. Through this study, we found that the FM-L21 is the most magnetic-structure stable phase for both Co2ZrAl and Co2ZrSi compounds, as well as they, are dynamically stable where all the calculated of the optic and acoustic phonon frequencies have positive values. Band structure calculation demonstrated that all compounds exhibit band gaps of about 0.88 and 1.54 eV using mBJ-GGA potentials for Co2ZrAl and Co2ZrSi in a localized minority spin channel (unlike the other direction which appears a metallic behavior) with high spin polarization (100%) in its ground state. Under high pressure, both compounds keep the same electronic behavior in both spins’ channels with a little decreasing in gap energy, unlike the total magnetic moment which doesn’t change. The semi-local Boltzmann transport theory has been used to investigate thermoelectric properties and we found that both compounds exhibit a high Seebeck coefficient and high-power factor up to 1.25 mV/K for Co2ZrSi. Also, the quasi-harmonic model has been applied to study the temperature effect on heat capacities at constant volume, in which entropy, Debye temperature and lattice thermal conductivity are analyzed and discussed. To get more information about the elastic behavior; the elastic stability in the equilibrium state and under two pressures values (12 GPa and 24 GPa) are found. The findings predicted the stability of these compounds’ properties with and without pressure, which makes them candidate materials for devices fabrication in several areas such as spinotronic, thermoelectric, shape-memory and spin filters.

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SABER Saad Essaoud , Ahmed S. Jbara, , (2021-04-10), First-principles calculation of magnetic, structural, dynamic, electronic, elastic, thermodynamic and thermoelectric properties of Co2ZrZ (Z = Al, Si) Heusler alloys, Journal of Magnetism and Magnetic Materials, Vol:531, Issue:, pages:167984, Elsevier

We have applied the pseudopotential plane wave method to study the effect of X element (X = Sn, Al and Hf atom) on the structural, elastic, electronic and thermodynamic properties of the ternary borides Sc3XB. We have employed the generalized gradient approximation (GGA) for the exchange and correlation potential. The equilibrium lattice constants and the bulk modulus and its pressure derivative are calculated and compared with available experiment and theoretical results. We have also predicted the elastic constants, Young's modulus (E), Poisson ratio (υ), shear modulus (G). SnBSc3 has the largest elastic moduli among the studied compounds. The contribution of the different bands was analysed from total and partial density of states curves. The bulk modulus, specific heats, and Debye temperature are calculated as a function of temperature and pressure using the quasi-harmonic Debye model.

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SABER Saad Essaoud , A. Benamer, Y. Medkour, S. Chaddadi, A. Roumili, , (2021-04-06), Ab-initio study of the structural, electronic, elastic and thermodynamic properties of Sc3XB (X=Sn, Al, Hf), Solid State Communications, Vol:331, Issue:, pages:114305, Elsevier

Manganese-based compounds are widely used, particularly those belonging to the 3d transition metals like MnAs, which has different properties so that it can crystallize in many structural phases and take a several magnetic states. With the help of ab-initio calculations, we carried out a theoretical study using the full potential linearized augmented plane wave method (FP-LAPW) based on the density functional theory (DFT) of the MnAs1-xPx alloy (0 ≤ x ≤ 1) in all different structural types and in different magnetic orders. In this study, we use both LDA and GGA approximations in the study of structural and magnetic properties while the mBJ approximation has been used in the electronic properties. First of all the structural-magnetic stability is initially identified then the parameters of the equilibrium lattice constant, the bulk modulus and the pressure phase transition were determined. The analysis of the electronic band structure and the spectra of the electronic density of states (DOS) are used to explain the behavior of the MnAs1-xPx alloys and to explore the nature of the bond between atoms. Through the calculation of the magnetic properties, we realized that the total and partial magnetism changes according to the structural phase and unit cell volume. We also explored and discussed the variation of some thermodynamic parameters versus temperature and pressure using the quasi-harmonic Debye model, this study allowed us to have a global idea of the effect of temperature and pressure on the macroscopic parameters such as the heat capacities Cv and Cp, the thermal expansion coefficient, the entropy and Debye temperature. The investigation of the properties of the studied compound allowed us to know if this material satisfies the norms and conditions of use in the systems of magnetic refrigeration.

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SABERSaad Essaoud , ,(2020-02-06); Les composés à base de manganèse : investigation théorique des propriétés structurales électroniques et magnétiques,Ecole Normale Supérieure - Kouba,

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SABER Saad Essaoud , ,(2019-11-13), Electronic and magnetic structure, elastic and thermal properties of Mn2-based full Heusler alloys,First international workshop on thermodynamic of metallic alloys,Batna University

Magnetism, electronic structure, elastic and thermal properties of Mn2YAl (with Y = Cr, V) have been investigated. The optimized lattice parameters, bulk modulus, and cohesive energy have been obtained. These alloys have the ferrimagnetic state as the most stable magnetic configuration, since the calculations showed a strong Mn-V antiferromagnetic coupling leading to the ferromagnetism of the Mn sublattices. A small and itinerant magnetic moment of Mn at the A site is found, which is antiparallel to the moment of Y at the B position in Mn2YAl (with Y = Cr, V) compounds. The calculated total spin moments are integral values and increase from − 2 μB/f.u. for Mn2VAl to – 1 μB/f.u. for Mn2CrAl with increasing the number of valence electrons. Band structure and total and partial density of states could be calculated via applying the modified Becke Johnson approximation (mBJ). Based on these results, Mn2YAl (with Y = Cr, V) are half-metallic ferrimagnets with the energy gap lies in the majority spin direction and a high-spin polarization (100%). The main difference between these two compounds is that the band gap is increased by 48% (0.210 eV for Mn2CrAl and 0.401 eV Mn2VAl). Elastic anisotropies, brittleness, and thermodynamic properties are determined for the Mn2YAl (with Y = Cr, V). The slight difference in the spatial distributions of Young’s moduli of Mn2YAl (with Y = Cr, V) reflects the small differences for the elastic anisotropies of the alloys under consideration. The mechanical stability of Mn2YAl (with Y = Cr, V) alloys are studied based on the elastic constants. The thermal properties are studied and investigated using the quasi-harmonic model, in addition, the temperature effect on heat capacities at constant pressure and volume, entropy, and thermal expansion are analyzed and discussed.

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SABER Saad Essaoud , Inshad Jum’h, H. Baaziz, Z. Charifi & Ahmad Telfah, , (2019-06-19), Electronic and Magnetic Structure and Elastic and Thermal Properties of Mn2-Based Full Heusler Alloys, Journal of Superconductivity and Novel Magnetism, Vol:32, Issue:, pages:3915–3926, Springer

Full potential band structure calculations have been performed on the NiAs (hexagonal), MnP (orthorhombic) and Zinc-blende structures of MnAs1−xPx (0 ≤ x ≤ 1) alloys. The stability of the ferromagnetic state is investigated by comparing the total energies for paramagnetic (P), ferromagnetic (F) and antiferromagnetic (AF) state, where different types of AF state are assumed. The stability of the different phases of MnAs1−xPx (0 ≤ x ≤ 1) is found to depend mainly on the volume and on the amount of magnetic order. It is found that for large lattice constants the ferromagnetic state is favored, whereas for small lattice constants different antiferromagnetic states can be stabilized. In the ferromagnetic state, the structure with minimal energy is always hexagonal, whereas it becomes orthorhombically distorted under pressure. The calculated total magnetic moment can be explained from the large charge transfer of electrons from the Mn cations to their neighbor As and P anions, and the strong p (As or P)-d(Mn) hybridization. We found that a particular Mn-Mn separation plays also the significant role in determining the change from antiferromagnetic to ferromagnetic order in such systems. It is also found a true half-metallic phase for zinc-blende MnAs and MnAs0.75P0.25 when the lattice constant expanded beyond 5 Å, otherwise, MnAs1−xPx (0 ≤ x ≤ 1) alloys were found to be metals.

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SABER Saad Essaoud , Z. Charifi, H. Baaziz, G. Uğur, Ş. Uğur,, , (2018-09-05), Electronic structure and magnetic properties of manganese-based MnAs1−xPx ternary alloys, Journal of Magnetism and Magnetic Materials, Vol:469, Issue:, pages:329-341, Elsevier

The objective of this work is the microscopic study of correlations in finite fermionic systems (by breaking the symmetry) via applying the HF + BCS and HTDA methods to the two light mirror nuclei 56Ni and 68Se. In the first part of this paper, we will make a comparison between the results obtained by the triaxial treatment and the ones obtained by the axial treatment. In the second part, we will compare the HTDA triaxial results with and without neutron-proton pairing correlations to the experimental ones

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SABER Saad Essaoud , , (2016-05-06), Microscopic Study of Correlations in Finite Fermionic Systems by Breaking the Axial Symmetry, International Journal of Modern Theoretical Physics, Vol:5, Issue:1, pages:8-21, modernscientificpress

Dans ce travail nous avons appliqué plusieurs méthodes (HF+BCS et HTDA) pour étudier la structure des deux noyaux (56Ni et 68Se).On a principalement abordé l’effet des corrélations dans les systèmes fermioniques finis en brisant la symétrie axiale. Dans la première partie, nous présentons les différents résultats obtenus pour les noyaux légers 56Ni et 68Se en utilisant l’approche HTDA axial et en les comparant avec ceux obtenus en brisant l’axialité(i.e. à l’aide de HTDA triaxial).Dans la seconde partie, nous traitons les corrélations d’appariement en s’appuyant sur la méthode HTDA sans et avec corrélations d’appariement neutrons- protons. Ces dernières sont habituellement négligées. Les résultats obtenus sont comparés aux résultats expérimentaux.

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SABER Saad Essaoud , ,(2016-04-10), ETUDE DE LA STRUCTURE DES NOYAUX 56Ni ET 68Se A L’AIDE DE L’ APPROXIMATION HTDA,The first workshop on matter and radiation “WMR2016”,Batna University

Récemment, les composés MnBi et MnSb sont parmi les matériaux utilisés pour produire des équipements de réfrigération. Cependant, les scientifiques ont effectué plusieurs études théoriques et des expérimentations afin d'étudier les propriétés structurales, électroniques, magnétiques et élastiques. Dans notre travail, nous avons étudié les propriétés structurales, électroniques, magnétiques et élastiques de MnBi et MnSb en utilisant la méthode FP-LAPW dans le cadre de la théorie de la fonctionnelle de la densité (DFT). Le terme du potentiel d'échange et de corrélation a été traité par deux différentes approximations LDA et GGA. Pour les Propriétés structurales, nous avons calculé les paramètres de la maille, le module de compressibilité. D’autre part, nous avons calculé la structure de bandes, la densité d'états totale et partielle et de la densité de charge et comparé les résultats obtenus avec d'autres calculs théoriques et expérimentales. On a calculé aussi le moment magnétique total et le moment magnétique de l’atome de manganèse. Enfin, on a défini aussi quelques paramètres élastiques comme le module de Young (E), le facteur d'anisotropie (A), le module de compressibilité adiabatique (Bs) et le module de cisaillement (G déformation résistance). La stabilité mécanique de ces matériaux a été traitée et exprimée a travers les constantes élastiques.

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SABER Saad Essaoud , ADMIN Admin , ,(2015-11-25), THEORITICAL STUDY OF SOME MATERIALS USED IN REFRIGERATION SYSTEMS,Second international conference on mechanics “ICM2015”,Costantine univrsity (Algeria)

In our calculations we employ the full potential–linearized augmented plane wave (FPLAPW)1 method within density functional theory (DFT)2-3 . The exchange-correlation potential was treated using the local density approximation (LDA)4 and the generalized gradient approximation (GGA)5. The structural parameters were investigated in zincblende type structure, the equilibrium lattice parameters, bulk moduli and the minimal energies were investigated and compared with the previous theoretical and experimental data. We have also determined the band-structure, total and partial density of states and the electron charge density. We calculated the elastic properties such as: the elastic constants, Young’s modulus E, the anisotropy factor A, the adiabatic modulus of compressibility Bs and the shear modulus G (deformation resistance). The mechanical stability of MnX (X= Bi, Sb) is studied as function of the elastic constants. Finally, the dependence of the isothermal bulk modulus (B) and the adiabatic bulk modulus (Bs) on pressure and temperature are investigated using the quasi-harmonic Debye model6. Also, the change of heat capacities at constant volume and pressure (Cv and Cp), the entropy and Debey temperature have been studied versus temperature

Citation

SABER Saad Essaoud , ,(2015-11-17), STRUCTURAL, ELECTRONIC, MAGNETIC ELASTIC AND THERMODYNAMIC PROPERTIES OF MnX (X=Bi,Sb),2) First international workshop on thermodynamic of metallic alloys “WITAM’2015”,Batna University

Recently, MnAs compound has got more and more attention since the discovery of the magneto- caloric effect[1]. Extensive theoretical and experimental studies were performed in order to investigate the structural, electronic and magnetic properties. In our calculations we employ the full potential— linearized augmented plane wave (FP-LAPW) method [2] which is based on density functional theory (DFT) [3-4]. The exchange - correlation potential was treated using the local density approximation (LDA) [5] and the generalized gradient approximation (GGA) [6]. The structural parameters were investigated in three phases : NiAs, MnP and zinc Blend type structures, the equilibrium lattice parameters, bulk modulus and the minimal energy were investigated and compared with the previous theoretical and experimental data. For the electronic properties we determined the band-structure, total and partial density of states and the electron charge density. Keywords: DFT, FP-LAPW, LDA, GGA, band structure calculations.

Citation

SABER Saad Essaoud , ,(2015-05-05), STRUCTURAL AND ELECTRONIC PROPERTIES OF MnAs IN DIFFERENT TYPE STRUCTURES,The first international conference on solar energy,Bordj Bou Arreridj university(Algeria)

Parmi les méthodes qui sont utilisées dans l’étude microscopique des noyaux atomiques il y a l’approximation de Hartree-Fock. Dans cette approche la fonction d’onde de l’état fondamental du noyau est recherchée sous la forme d’un déterminant de Slater construit à partir des fonctions d’onde individuelles des nucléons dans le cadre de l’approximation de particules indépendantes. La méthode de Hartree-Fock-Bogoliubov (HFB) permet de prendre en compte les corrélations d’appariement à partir de la fonction d’onde de HF de l’état fondamental du noyau. Le traitement de l’appariement à la "BCS" (Bardeen-Cooper et Schrieffer) ne conservant pas le nombre de particules pour cela on applique la méthode HTDA ou « Higher-Tamm-Dancoff Approximation ». Cette approche fournit une description simple et une interprétation claire des corrélations au-delà du champ moyen dans une approche de type Modèle en Couches tronqué. Dans le dernier chapitre nous présentons les différents résultats que nous avons obtenus par l’application du traitement HTDA axial et sa comparaison avec le traitement HTDA triaxial aux noyaux légers 56Ni et 68Se, et l’application de la méthode HTDA sans et avec les corrélations d’appariement neutrons- protons et on compare les résultats obtenus aux résultats expérimentaux.

Citation

SABERSaad Essaoud , ,(2013-03-07); Etude microscopique des corrélations dans les systèmes fermioniques finis en brisant la symétrie axiale,Ecole Normale Supérieure - Kouba,