MOHAMMED ELAMIN Ketfi

GADIRI Fatiha , MAKHLOUF Donya

Prédiction ab-initio des propriétés structurales, électroniques et optiques des composés fluoro-pérovskites ABF3

Zoubiri Marwa , LAKEHAL Malika

Etude et adaptation des méthodes d’alignement en tomographie électronique, application aux images microscopiques

MIRA Nesrine , BOUKHADEM Oumesaad

Etude des propriétés optoélectroniques du matériau ternaire emplecitite CuBiS2 pour des applications photovoltaïques

BARKA Mohamed , BEN CHETOUH Chaima

Mise en oeuvre et évaluation des méthodes d'alignement en tomographie électronique : Applications aux images microscopiques

RAHLI Boubaker , ADJABI Kamel

Etude et adaptation d'un bras manipulateur en traitement d'image à trois degrés de liberté

DHIMI Belkassem , AOUINA elmouayed billeh

Etude, Adaptation et réalisation d'un système électronique pour sauver de vie des infarctus "accident Cardiaque"

AMROUNE Ilyes

Méthodes d'alignement en tomographie électroniques -Applications aux images microscopiques

MESSAK abdelmoulaim

Processus d'alignement des séries d'image microscopique à niveau de gris

Density functional theory with the Hubbard corrective coefficient for the cobalt (Co) and iron (Fe) atoms was adopted to calculate the structural, dynamic, and magnetic properties of the KCoF3 and KFeF3 perovskites. The Hubbard coefficients for Fe and Co atoms were calculated using the Madsen method and their value are 3.456 eV and 4.025 eV, respectively.The structural stability of these compounds was verified by calculating their negative enthalpies of formation at the most stable state and under the influence of pressure up to 30 GPa. Their dynamic stability was confirmed via the calculation of the phonon dispersions along the high symmetry lines in the first Brillouin region. The temperature dependence of the thermal expansion coefficient, isochoric heat capacity, entropy, and lattice thermal conductivity were calculated for various fixed pressures of 0, 10, 20 and 30 GPa. Temperature dependence of the single crystal and polycristalline elastic moduli were predicted for a temperature range of 0–1000 K.

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MOHAMMED ELAMIN KETFI , , (2024-07-02), DFT + U based characterization of structural, magnetic, dynamic, elastic and thermodynamic properties of KXF3 (X = Fe or Co) halide perovskites compounds, Chemical Physics Letters, Vol:850, Issue:141455, pages:9, Elsevier

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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MOHAMMED ELAMIN KETFI , , (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:114721, pages:10, 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 3.3lB 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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MOHAMMED ELAMIN KETFI , , (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:12648, Issue:3264, pages:8, Springer

In this study, we present a comprehensive exploration of the Delafossite composites using density functional theory (DFT) and the semi-classical Boltzmann simulations within the Wien2k framework. Our investigation includes structural, electronic, magnetic and thermal properties in the tetragonal phase, providing a holistic understanding of these materials. Firstly, the structural-magnetic stability of XMnZ2 (X = Au, Hg, and Tl, Z = S, Se) was verified through ground-state energy calculations obtained from structural optimizations. Our results indicate a stable ferromagnetic phase for the six compounds. Moving on to electronic properties, we utilize the Trans-Blaha modified Becke Johnson (TB-mBJ) functional potential to elucidate the electronic behavior (metallic, half metallic, semiconductor or insolating) of the considered compounds in both up and down spin directions. Furthermore, spin-polarized band structures unveil a net magnetism in the range of 2.67μB to 4.02μB, highlighting the potential for spintronics applications. Finally, we investigate the thermodynamic properties 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. Overall our study provides a comprehensive understanding of the multifaceted properties of Delafossites, paving the way for their potential applications in various fields.

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MOHAMMED ELAMIN KETFI , , (2024-05-18), DFT Study of Structural, Electronic, Magnetic and Thermodynamic properties of XMnZ2 (X = Au, Hg, and Tl, Z = S, Se) Delafossites, Journal of Inorganic and Organometallic Polymers and Materials, Vol:10904, Issue:3142, pages:10, Springer

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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MOHAMMED ELAMIN KETFI , , (2024-01-30), 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:10904, Issue:3060, pages:18, Springer

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 Youngs 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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MOHAMMED ELAMIN KETFI , SABER SAAD ESSAOUD , Said M Al Azar, Anas Y Al-Reyahi, Ahmad A Mousa and Nabil Al-Aqtash5, , (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:15908, pages:15, IOPscience

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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MOHAMMED ELAMIN KETFI , , (2023-11-30), 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:107435, pages:10, 2023 Elsevier B.V

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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MOHAMMED ELAMIN KETFI , , (2023-11-30), Insight into physical properties of lutetium-based double half-Heusler alloys LuXCo2Bi2 (X = V, Nb and Ta), Journal of Rare Earths, Vol:1, Issue:1, pages:10, 2023 Elsevier B.V

The Delafossite group of oxide materials was initially uncovered in 1965, comprising a category of ternary compounds characterized by the general formula ABO2, with A and B denoting metallic elements. One of the most prevalent Delafossites is CuAlO2, which stands as a p-type semiconductor known for its remarkable electrical conductivity and transparency across the visible and near-infrared regions of the electromagnetic spectrum [1–3]. These distinctive qualities have propelled Delafossite materials into the spotlight for a wide array of applications, including use in electronic devices, energy storage, energy conversion, and optoelectronics. Their intriguing electronic, magnetic, and optical attributes have only recently garnered attention [4,5], prompting researchers to delve into these materials, not only to grasp their fundamental properties but also to uncover potential applications. Density functional theory (DFT) calculations have unveiled a range of electronic band structures within Delafossites, varying from metals to semiconductors contingent upon the specific choice of A and B ions. Furthermore, DFT calculations have forecasted that particular Delafossites, such as CuCrO2 and CuFeO2[6,7], manifest antiferromagnetic ordering due to the interplay of spins on the transition metal ions. In an ab initio study conducted by Azmat et al. [8], it was demonstrated that CuXO2 compounds (where X represents Al, Ga, In, B, La, Sc, Y) display semiconductive behavior. Experimental investigations into Delafossites have encompassed the electronic and optical properties. Among the most renowned Delafossites is CuAlO2, renowned for its high electrical conductivity and optical transparency. CuAlO2 boasts exceptional carrier mobility and low carrier concentration, making it an ideal candidate for transparent conductive electrodes in optoelectronic devices. Additionally, Delafossites have undergone scrutiny for their photovoltaic potential, with CuInO2 and CuGaO2 exhibiting promising results for solar cell applications. An experimental study by Kushwaha et al. [9] explored the PdRhO2 compound, revealing its crystallization in a rhombohedral-type structure characterized by crystal cell dimensions of a = 3.0240 Å and c = 18.096 Å. In this study, we perform first-principles calculations based on density functional theory and the semi-classical Boltzmann method to investigate the structural, optoelectronic, magnetic, thermodynamic and thermoelectric properties for BrCdO2 in the Tetragonal phase. To compute the structural properties, the Wang and the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) was used as exchange-correlation potentials. Besides, the modified Becke-Johnson functional of Tran and Blaha (TB-mBJ) are used to compute the electronic and optical properties to achieve the best band gap energy values and a higher degree of precision. Our calculations have revealed that this compound have direct band gap 4.17 eV. As a result of this study, BrCdO2 is promising material for optoelectronic devices, especially as photovoltaic materials in solar cells.

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MOHAMMED ELAMIN KETFI , ,(2023-11-28), Theoretical analysis of structural, optoelectronic and magnetic properties of ABO2 Delafossite semiconductor,1st International Conference on Physico-chemistry, Materials Sciences & Applied Mathematics,Université de Skikda

ABO2 is a type of Delafossite compound that has been investigated for their electronic properties, such as high electrical conductivity and magnetic behavior; make them promising candidates for use in electronic devices. In this study, we perform first-principles calculations based on density functional theory and the semi-classical Boltzmann method to investigate the structural, optoelectronic, magnetic, thermodynamic and thermoelectric properties for MgNiO2 in the Tetragonal phase. To compute the structural properties, the Wang and the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) was used as exchange-correlation potentials. Besides, the modified Becke-Johnson functional of Tran and Blaha (TB-mBJ) are used to compute the electronic and optical properties to achieve the best band gap energy values and a higher degree of precision. Our calculations have revealed that this compound have direct band gap 1.79 eV. As a result of this study, MgNiO2 is promising material for optoelectronic devices, especially as photovoltaic materials in solar cells.

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MOHAMMED ELAMIN KETFI , ,(2023-11-17), AN AB INITIO ANALYSIS OF STRUCTURAL, OPTOELECTRONIC AND MAGNETIC PROPERTIES OF ABO2 DELAFOSSITE SEMICONDUCTOR,IV-INTERNATIONAL SIIRT CONFERENCE ON SCIENTIFIC RESEARCH,Siirt University - Turkey

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.

Citation

MOHAMMED ELAMIN KETFI , , (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:111733, pages:15, 2023 Elsevier B.V

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

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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MOHAMMED ELAMIN KETFI , , (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:1, pages:18, Springer

In this work, we performed first-principles calculations based on density functional theory (DFT) 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 direct band gaps in the range of 1.87 to 2.58 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 as 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 K to 500 K. The relaxation time and lattice thermal conductivity are calculated as well. Our results reveal that low thermal conductivity and 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.

Citation

MOHAMMED ELAMIN KETFI , , (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:1013, pages:15, Springer

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.

Citation

MOHAMMED ELAMIN KETFI , , (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:414809, pages:10, 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.

Citation

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

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

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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MOHAMMED ELAMIN KETFI , ,(2021-04-21), PRESSURE EFFECT ON THE MAGNETIC, ELECTRONIC AND ELASTIC STABILITY OF SOME MATERIALS USED IN THERMO-ELECTRIC GENERATORS,1st International Conference on Sustainable Energy and Advanced Materials IC-SEAM’21 April 21-22, 2021, Ouargla, ALGERIA (Virtual conference),UNIVERSITY OF KASDI MERBAH OUARGLA

We used density functional theory based calculations to investigate the structural and optic properties of copper-based ternary chalcogenide Cu-M-X (M : Sb, Bi & X : S, Se). These form orthorhombic crystallographic structure with Pnma space group. The calculated electronic band structure is indirect for all these compounds in conjunction with a close direct band gap transition. Interestingly, a very high optical absorption coefficient above 105 cm-1 above band gap values is noticed for these materials, making them suitable for ultrathin solar cell absorbers.  

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MOHAMMED ELAMIN KETFI , Hamza BENNACER , SERAI Housseyn, ,(2019-12-26), Ab-initio study on optical properties of CuBiS2-Based solar cells applications,1er Atelier National sur WIEN2k,MOSTAGANEM