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16. Structural, elastic, electronic and optical properties of the half-Heusler ScPtSb and YPtSb compounds under pressure

Author

Radjai, M., Bouhemadou, A., and Maouche, D.

Subjects
Condensed Matter - Materials Science
Abstract

First-principles calculations using the plane-wave pseudopotential method within the generalized gradient approximation method were performed to study the pressure dependence of the structural, elastic, electronic and optical properties for the half-Heusler compounds ScPtSb and YPtSb in a cubic MgAgAs-type structure. The calculations were performed with the inclusion of spin-orbit coupling. The calculated equilibrium lattice parameters are in good agreement with the available experimental and theoretical values. The crystal rigidity and mechanical stability were discussed using the elastic constants and related parameters, namely bulk modulus, shear modulus, Debye temperature, Poisson's coefficient, Young's modulus and isotropic sound velocities. The calculated electronic band structures show that ScPtSb has an indirect gap of $\Gamma-X $ type, whereas YPtSb has a direct band gap of $\Gamma -\Gamma $ type. Furthermore, the effect of pressure on the optical properties, namely the dielectric function, absorption spectrum, refractive index, extinction coefficient, reflectivity and energy-loss spectrum is investigated for both compounds ScPtSb and YPtSb., Comment: 16 pages, 13 figures, 3 tables

Published
2021
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21. FP-LAPW study of structural, magnetic, electronic, elastic, and thermoelectric properties of CoCrS Half-Heusler compound

Author

Noorhan F. AlShaikh Mohammad, Mohammed S. Abu-Jafar, Jihad H. Asad, Mahmoud Farout, A. Bouhemadou, Ahmad A. Mousa, R. Khenata, Nazia Erum, and Abdullah Chik

Subjects
Physics, QC1-999
Abstract

The present article has utilized the WIEN2k computational code to examine the structural, elastic, electronic, magnetic, thermoelectric, and dynamic aspects of the CoCrS Half-Heusler (HH) compound. In this work, calculations have been performed by utilizing the full-potential linearized augmented plane wave method using density functional theory. The electronic bandgap was better interpreted by using the modified Becke–Johnson exchange–correlation functional. We evaluated various electronic properties of the CoCrS HH compound, including band structure plots and density of states. Furthermore, we examined the magnetic characteristics through the computation of magnetic moments and the examination of the spin-polarized electronic state behavior. We also determined the elastic properties of the CoCrS HH compound. These properties, which include stiffness, resilience, and general stability, provide important information about how the material responds to mechanical deformation. Moreover, we explored the electronic structure and found that type 5 of CoCrS exhibits a metallic behavior. In addition, we examined the compound’s thermoelectric properties. Finally, the dynamical properties indicate that type 5 of CoCrS is dynamically stable.

Published
2024
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22. Half-metallicity from CrCoSi and MnCoSi half-Heusler alloys to their derivative double half-Heusler CrMn[Co.sub.2][Si.sub.2]

Author

Elarabi, Hiba, Khelfaoui, Friha, Boudia, Keltouma, Labani, Fatima, Hamlat, Mama, Sadouki, Ouafaa, Belkharroubi, Fadila, Faid, Fares, Bouhemadou, Abdelmadjid, and Deghfel, Bahri

Subjects
Silicon alloys -- Mechanical properties -- Magnetic properties -- Electric properties, Density functionals -- Usage, Cobalt alloys -- Mechanical properties -- Magnetic properties -- Electric properties, Spintronics -- Research, Physics
Abstract

The structural, elastic, electronic, and magnetic properties of the CrCoSi, MnCoSi parent half-Heusler (HH) alloys, and their CrMn[Co.sub.2][Si.sub.2] derivative double half-Heusler (DHH) compound are studied, utilizing the augmented plane wave method, which is based on density functional theory and implemented in the WIEN2k code. The stability of HH structure of the CrCoSi and MnCoSi alloys has been checked for their non-magnetic and ferromagnetic phases, leading to that the latter phase of the type I arrangement is the most stable. The CrMn[Co.sub.2][Si.sub.2] DHH alloy, derivative from the found structural and magnetic ground states of CrCoSi and MnCoSi HH alloys, is constructed and investigated. This DDH as well as its CrCoSi parent HH are found to be resistant to deformation and can be classified as ductile materials, whereas the MnCoSi compound is brittle. By the gradient generalized approximation (GGA), the electronic structures of CrCoSi, MnCoSi, and CrMn[Co.sub.2][Si.sub.2]compounds exhibit a metallic behavior in the spin-up channel and a semiconducting behavior in the spin-dn channel, with band gaps (half-metallic gaps) of 0. 851(0.020), 0.852(0.021), and 0.531(0.002) eV, respectively. The half-metallicity of CrMn[Co.sub.2][Si.sub.2] DHH is retained with smaller (larger) band gap (half-metallic gap) of 0.38(0.106) eV than that of GGA, using GGA + U approximation. In addition, the total magnetic moments are found to be 1, 2, and 3 [[mu].sub.B] for CrCoSi, MnCoSi, and CrMn[Co.sub.2][Si.sub.2], respectively. Therefore, these alloys can be good candidates for spinitronic applications due to their half-metallicity. Key words: half-metal, heusler alloys, spin polarization, mechanical stability, FP-LAPW, 1. Introduction Spin-based electronics has grown into a significant field of study that spans a wide range of high spin-polarized materials, used in spintronic devices. It overcomes the limitations of [...]

Published
2023
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24. DFT Insights into the Physical Properties of Layered LiMnSe2 and LiMnTe2 Compounds

Author

Abdennour Benmakhlouf, Fares Faid, Nedjmeddine Ghermoul, Kemal Özdoğan, Taoufik Helaimia, Abdelmadjid Bouhemadou, and Iosif Galanakis

Subjects
first-principles calculations, electronic band structure, ferromagnetism, half-metal, elastic properties, Slater–Pauling, Mining engineering. Metallurgy, TN1-997
Abstract

Using state-of-the-art first-principles electronic-band-structure calculations alongside density functional theory, we investigated the structural, elastic, electronic, and magnetic properties of LiMnZ2 (Z = Se, Te) compounds with a trigonal structure. Initially, we determined the equilibrium lattice structure and atomic positions, which aligned well with experimental values. Ferromagnetism was shown to be more favorable than the non-magnetic state. The elastic constants, cohesive energies, and formation energies indicated that the studied compounds were mechanically stable in the experimentally determined trigonal lattice. The analysis of spin-polarized band structures and density of states revealed that both LiMnZ2 compounds exhibited perfect half-metallic characters. The total spin magnetic moment per formula unit adhered to the Slater–Pauling rule, being exactly 4 μΒ, mainly concentrated at the Mn atoms due to the strong spin polarization of the Mn d orbitals. We anticipate that our results will prompt further experimental and computational studies for the application of these layered materials in practical devices.

Published
2024
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36. Structural, electronic and magnetic properties of the Manganese telluride layers AMnTe2 (A=K, Rb, Cs) from first-principles calculations

Author

Benmakhlouf, A., Bourourou, Y., Bouhemadou, A., Bentabet, A., Khemloul, F., Maabed, S., Bouchenafa, M., and Galanakis, I.

Subjects
Condensed Matter - Materials Science
Abstract

Using first-principles electronic structure calculations based on density functional theory (DFT), we investigate the structural, electronic and magnetic properties of the layered ternary manganese tellurides: AMnTe2 (A = K, Rb, and Cs). Calculations are accomplished within the full-potential linearized augmented plane wave (FP-LAPW) using the generalized gradient approximation GGA formalism for the exchange correlation term. We have treated all ferromagnetic, antiferromagnetic and non-magnetic phases and found that the ferromagnetic is the ground-state for all studied compounds. Moreover, all three compounds under study are half-metals with a total spin magnetic per formula unit of 4 mu_B which is mainly localized at the Mn atoms. We express for these compounds a new version of the Slater-Pauling rule and discuss in detail the origin of the minority-spin gap. Finally, we have also calculated some other relevant quantities such as the bulk modulus B, the pressure derivative B', the virtual semiconducting gap Eg, and the half-metallic gap E_HM.

Published
2018
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45. New Pressure-Induced Polymorphic Transitions of Anhydrous Magnesium Sulfate

Author

Benmakhlouf, A., Errandonea, D., Bouchenafa, M., Maabed, S., Bouhemadou, A., and Bentabet, A.

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

The effects of pressure on the crystal structure of the three known polymorphs of magnesium sulfate have been theoretically study by means of DFT calculations up to 45 GPa. We determined that at ambient conditions gamma MgSO4 is an unstable polymorph, which decompose into MgO and SO3, and that the response of the other two polymorphs to hydrostatic pressure is non isotropic. Additionally we found that at all pressures beta MgSO4 has a largest enthalpy than alpha MgSO4. This indicates that beta MgSO4 is thermodynamically unstable versus alpha MgSO4 and predicts the occurrence of a beta alpha phase transition under moderate compression. Our calculations also predict the existence under pressure of additional phase transitions to two new polymorphs of MgSO4, which we named as delta MgSO4 and epsilon MgSO4. The alpha delta transition is predicted to occur at 17.5 GPa, and the delta epsilon transition at 35 GPa, pressures that nowadays can be experimentally easily achieved. All the predicted structural transforma ions are characterized as first order transitions. This suggests that they can be non reversible, and therefore the new polymorphs could be recovered as metastable polymorphs at ambient conditions. The crystal structure of the two new polymorphs is reported. In them, the coordination number of sulfur is four as in the previously known polymorphs, but the coordination number of magnesium is eight instead of six. In the article we will report the axial and bond compressibility for the four polymorphs of MgSO4. The pressure volume equation of state of each phase is also given. The values obtained for the bulk modulus are 62 GPa, 57 GPa, 102 GPa, and 119 GPa for alpha MgSO4, beta MgSO4, delta MgSO4, and epsilon MgSO4, respectively. Finally, the electronic band structure of these four polymorphs of MgSO4 has been calculated by the first time., Comment: 35 paginas, 9 figures, Table 9

Published
2017
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46. Density functional theory investigation of the phase transition, elastic and thermal characteristics for AuMTe2(M = Ga,In) chalcopyrite compounds.

Author

Boucerredj, N., Semari, F., Ghemid, S., Oughaddou, H., Khenata, R., Bouhemadou, A., Boucharef, M., Meradji, H., Chouahda, Z., Bin-Omran, S., and Goumri-Said, S.

Abstract

We explored the pressure‐induced structural phase transitions and elastic properties of AuMTe2 (M = Ga,In) using the full‐potential linearized augmented plane wave method within the framework of density functional theory, applying both generalized gradient and local density approximations. Thermodynamic properties were further assessed through the quasi‐harmonic model. We determined the transition pressures for the phase shift from the chalcopyrite structure to the NaCl rock‐salt phase in both AuGaTe2 and AuInTe2. Additionally, we calculated and analyzed mechanical properties, such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy, ductility versus brittleness, and hardness for the polycrystalline forms of AuMTe2 (M = Ga,In). The study also examined how temperature and pressure affect the Debye temperature, heat capacities, thermal expansion, entropy, bulk modulus, Grüneisen parameter, and hardness, utilizing the quasi‐harmonic Debye model. [ABSTRACT FROM AUTHOR]

Published
2024
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