Browsing by Author "Soyalp, F."

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Ab Initio Investigation of the Structural, Electronic and Optical Properties of Cubic Gaas1-X P X Ternary Alloys Under Hydrostatic Pressure
(Springer, 2015) Moussa, R.; Abdiche, A.; Abbar, B.; Guemou, M.; Riane, R.; Murtaza, G.; Soyalp, F.
The structural, electronic and optical properties of the GaAs1-x P (x) ternary alloys together with their binary GaP and GaAs compounds were investigated in the zinc-blende (ZB) phase using the density functional theory. The lattice constant of the GaAs compound decreases while its bulk modulus increases when the doping concentration of the P dopant is increased. In addition, both parameters (lattice constant and bulk modulus) show small deviations from the linear concentration dependence. The energy band gap of the GaAs compound is of the direct nature, which increases with the increase in the P dopant concentration, whereas at higher P dopant concentration, the band gap shifts from direct to indirect character. On the other hand, the hydrostatic pressure has a significant effect on the band structure of the investigated compounds where the binary GaAs compound changes from a direct band gap semiconductor to an indirect band gap semiconductor at P a parts per thousand yen 5 GPa. Furthermore, the pressure-dependence of the optical properties of the GaAs, GaP and GaAs0.75P0.25 alloy were also investigated, where the calculated zero frequency refractive index and the dielectric function are also compared with the experimental results as well as with different empirical models.
Ab Initio Investigations of Phonons and Thermodynamic Properties of Sczn and Yzn in the B2 Structure
(Elsevier, 2013) Soyalp, F.; Yavuz, M.; Yalcin, Z.
We have performed an ab initio investigation of structural, elastic, electronic, lattice dynamical, and thermodynamic properties of ScZn and YZn in B2 structure. The calculations was conducted within the density functional theory and linear response theory using the pseudopotentials and a plane wave basis set. The completely minimized structural parameters and elastic constants of ScZn and YZn compounds are in excellent agreement with previous theoretical and experimental data. The calculated phonon dispersion relations for YZn concur very well with experimental data available for main symmetry directions. Through the full quasi harmonic model, in which the phononic effects considered, the thermodynamic properties such as temperature dependence of the isothermal and adiabatic bulk modulus, thermal expansion coefficients, heat capacities, entropy and free energy have been successfully calculated in the whole temperature range from 0 to 1000 K. (c) 2013 Elsevier B.V. All rights reserved.
Ab Initio Investigations of the Structural, Electronic, Magnetic and Mechanical Properties of Crx (X = As, Sb, Se, and Te) Transition Metal Pnictides and Chalcogenides
(Iop Publishing Ltd, 2019) Charifi, Z.; Guendouz, D. J.; Baaziz, H.; Soyalp, F.; Hamad, B.
The structural, electronic, magnetic, and mechanical properties of CrX (X = As, Sb, Se and Te) transition metal pnictides and chalcogenides were investigated using ab initio density functional theory using the local density approximation and generalized gradient approximation. Under ambient conditions, CrAs and CrTe are stable in the orthorhombic MnP (MP)-type antiferromagnetic (AFM) and hexagonal NiAs (NA) (FM) structures, respectively, whereas CrSb and CrSe have NA-type (AFM) structure. The half-metallic behavior was predicted for the zinc blende (ZB) and wurtzite (WZ) structures of CrAs, the zinc blende (ZB)-type of CrSb and CrSe compounds and the zinc blende (ZB) and rock salt (RS) structures of CrTe. However, the remaining structures are found to exhibit a metallic behavior. The highest total magnetic moment of 4 mu(B) was predicted for the RS and ZB (FM) structures of CrTe. The investigated CrX compounds were found to be mechanically stable at ambient pressure. The high value of B/G ratio indicates that CrSb (NA) is a ductile material, whereas CrAs (MP), CrSe and CrTe (NA) are brittle due to the lower B/G value.
Computational Investigations on Band Structure and Electronic Features of Chromium-Based Carbides and Nitride Cr3px (X = C and N) Through the Fp-Apw Plus Lo Approach
(Academic Press Ltd- Elsevier Science Ltd, 2017) Seddik, T.; Ugur, G.; Soyalp, F.; Khenata, R.; Prakash, Deo; Kityk, I. V.; Verma, K. D.
In this work, we have theoretically investigated the band structure of antiperovskite chromium-based carbides and nitrides Cr3PX (X = C and N) using the first-principles calculation based on the FP-APW+LO method. The principal structural properties i.e., lattice constants (a,b,c) and internal parameters are in accordance with the experimental results. The calculated values of elastic constants indicated that the mechanical strength for both Cr3PC and Cr3PN compounds at (001) plane is higher than the (100) and (010) planes. Moreover, the Cr3PX compounds are expected to be hard materials with ductile nature. In addition, we have found that the FM ground state of herein materials Cr3PC and Cr3PN are energetically favorable with low magnetic moments of about 2.27 and 2.94 AB, respectively, confirming that these are weak ferromagnets. Based on the spin-polarized electronic band structure we have found that both alloys have metallic behavior, such behavior has been shown in the calculated electrical conductivity. We have also estimated other thermoelectric constants like the Seebeck coefficient, thermal conductivity, power factor and electrical resistivity of Cr3PC and Cr3PN compounds. (C) 2016 Published by Elsevier Ltd.
Computational Investigations on Band Structure and Optical Properties of the Besexte1-X Alloys Through the Fp-Lapw Approach
(Elsevier Gmbh, 2017) Hadji, K.; Abdiche, A.; Soyalp, F.; Bin Omran, S.; Khenata, R.
In this paper, we have theoretically explored the structural, electronic and optical properties of the zinc blende structure of ternary alloys using the full-potential linearized augmented plane wave (FP-LAPW) method within the density-functional theory (OFF) as implemented in the Wien2 K code. The electronic properties were computed using the following two approximations: the generalized gradient approximation (GGA) and the Tran-Blaha-modified Becke-Johnson potential (TB-mBJ). The obtained results clearly show that ternary alloys exhibit large and direct band gaps while binary compounds are indirect band gap semiconductors. (C) 2016 Elsevier GmbH. All rights reserved.
A Dft Study of the Electronic and Magnetic Properties of Fe2mnsi1-Xgex Alloys
(Elsevier, 2012) Hamad, B.; Charifi, Z.; Baaziz, H.; Soyalp, F.
We performed density functional theory (DFT) calculations to study the structural, electronic and magnetic properties of Fe2MnSi1-xGex alloys (x=0, 0.25, 0.50, 0.75, and 1.00). The lattice constant is found to increase linearly as a function of Ge concentration with a decrease in the formation energy. The total magnetic moment is found to be 3 mu(B) for all alloys with the most contribution from Mn local magnetic moments. Iron atoms, however, exhibit much smaller spin moments about 10% of the bulk value. It seems that due to the proximity of Fe, magnetic moments have been induced on the sp atoms, which couple antiferromagnetically with Fe and Mn spin moments. Although, the band gap remains almost constant (0.5 eV), the spin-flip gap decreases as a function of x. (C) 2012 Elsevier B.V. All rights reserved.
Dft-Based Ab Initio Study of the Electronic and Optical Properties of Cesium Based Fluoro-Perovskite Csmf3 (M = Ca and Sr)
(World Scientific Publ Co Pte Ltd, 2012) Harmel, M.; Khachai, H.; Ameri, M.; Khenata, R.; Baki, N.; Haddou, A.; Soyalp, F.
Density functional theory (DFT) is performed to study the structural, electronic and optical properties of cubic fluoroperovskite AMF(3) (A = Cs; M = Ca and Sr) compounds. The calculations are based on the total-energy calculations within the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential is treated by local density approximation (LDA) and generalized gradient approximation (GGA). The structural properties, including lattice constants, bulk modulus and their pressure derivatives are in very good agreement with the available experimental and theoretical data. The calculations of the electronic band structure, density of states and charge density reveal that compounds are both ionic insulators. The optical properties (namely: the real and the imaginary parts of the dielectric function epsilon(omega), the refractive index n(omega) and the extinction coefficient k(omega)) were calculated for radiation up to 40.0 eV.
Effect of Octahedral Cation on Electronic, Magnetic and Optic Properties of Cox2o4 (X = Cr, Mn and Fe) Spinel Compound
(Taylor & Francis Ltd, 2022) Hetache, N.; Charifi, Z.; Ghellab, T.; Baaziz, H.; Soyalp, F.
The magnetic, structural and optical properties of CoX2O4 (X = Cr, Mn and Fe) spinels are calculated using GGA + U approximation. The effect of the octahedral cation X on the properties of these spinels are analyzed. In order to better understand the electronic aspect of these compounds we studied the issue between the relative forces of the exchange effect and the crystal field effect through a complete analysis of the densities of electronic states. Obtaining the correct ground state is only possible if the electron-electron interactions between magnetic cations are introduced. When the X cations are changed, the crystalline structure changes totally from cubic normal spinel for CoFe2O4 to tetragonal normal spinel one for CoMn2O4 to inverse spinel for CoCr2O4. The electronic properties of our spinels are significantly different, an increase in the band gap from Fe to Mn to Cr compounds is obtained. Magnetic exchange interactions are strongly affected by sub-lattices occupation in the inverse phase of CoFe2O4 and significant structural distortion of the CoMn2O4 compound. The analysis of structural parameters and electronic structures plays a role on the trends of magnetic exchange interactions. We have noticed that the iron states in CoFe2O4 are extremely localised making this spinel very different from the X cation states in the other two spinels. So the variation in X cations allows us to confirm the trend in the properties of CoX2O4. The prediction of optical properties is possible and it allowed us to calculate different optical parameters. We have noticed that epsilon(1)(0) decreases with increasing band gap.
Elastic, Electronic, Chemical Bonding and Thermodynamic Properties of the Ternary Nitride Ca4tin4: Ab Initio Predictions
(Elsevier Science inc, 2019) Boucenna, S.; Haddadi, K.; Bouhemadou, A.; Louail, L.; Soyalp, F.; Khenata, R.
In order to shed light on the unexplored properties of the ternary nitride Ca4TiN4, we report for the first time the results of an ab initio study of its structural, electronic, elastic, chemical bonding and thermodynamic properties. Calculated equilibrium structural parameters are in excellent concordance with available experimental data. Electronic properties were explored through the calculation of the energy band dispersions and density of states. It is found that Ca4TiN4 has an indirect band gap (Z-Gamma) of 1.625 (1.701) eV using LDA (GGA). Nature of the chemical bonding was studied via Mulliken population analysis and charge density distribution map. It is found that the Ca-N bond is dominantly ionic, whereas the Ti-N one is dominantly covalent. Elastic properties of both single-crystal and polycrystalline phases of the title compound were explored in details using the stain-stress approach. Analysis of the calculated elastic moduli reveals that the title compound is mechanically stable, ductile and elastically anisotropic. Temperature and pressure dependencies of the unit-cell volume, bulk modulus, heat capacities, volume thermal expansion coefficient, Gruneisen parameter and Debye temperature were investigated based on the quasiharmonic Debye model. (C) 2019 Published by Elsevier Inc.
Electronic Structure Calculations of Rare-Earth Intermetallic Compound Yag Using Ab Initio Methods
(Elsevier Science Bv, 2009) Ugur, S.; Ugur, G.; Soyalp, F.; Ellialtioglu, R.
The structural, elastic and electronic properties of YAg-B2(CsCl) were investigated using the first-principles calculations. The energy band structure and the density of states were studied in detail, including partial density of states (PDOS), in order to identify the character of each band. The structural parameters (lattice constant, bulk modulus, pressure derivative of bulk modulus) and elastic constants were also obtained. The results were consistent with the experimental data available in the literature, as well as other theoretical results.
Electronic Structure, Phase Stability, Vibrational and Thermodynamic Properties of the Ternary Nowotny-Juza Materials Limgsb and Liznsb
(Elsevier Science Bv, 2017) Guendouz, Dj.; Charifi, Z.; Baaziz, H.; Soyalp, F.; Ugur, G.; Ugur, S.
A comprehensive study of structure, phase stability, electronic, vibrational and thermodynamic properties of LiMgSb and LiZnSb compounds is performed by carrying out First-principles calculations within densityfunctional theory using the full potential linearized augmented plane wave (FP-LAPW) combined with the pseudo-potential method. The generalized-gradient approximation (GGA) and the local density approximation (LDA) are chosen for the exchange-correlation energy. The Engel-Vosko (EV-GGA) formalism and mBJ approach are applied for the electronic properties. By exchanging the position of the atoms in the cubic structure, three phases (alpha, beta, gamma) are composed. Under ambient conditions, LiMgSb is stable in the cubic a structure however LiZnSb in the wurtzite one. At high pressure, these compounds undergo a structural phase transition from the cubic alpha to cubic gamma phase for LiMgSb and from the wurtzite to cubic gamma phase for LiZnSb, and the transition pressures were calculated. The quasi-harmonic Debye model, in which the phononic effects are predicted, is applied to the investigate of the thermodynamic properties. The temperature effect on the volume V(T), bulk modulus, B(T), thermal expansion coefficient alpha(T), specific heats (C-V and C-p) and Debye temperatures Theta(D), in different pressure and temperature range from 0 to 1000 K are investigated. Our results are in good agreement with previous theoretical calculations and the available experimental data. The band structure, density of states (DOS), and phonon dispersion curves have been obtained and analyzed.
Electronic, Optical, and Thermoelectric Properties of Vacancy-Ordered Double Perovskite K2snx6 (X = Cl, Br, I) From First-Principle Calculations
(Institute of Physics, 2024) Zikem, A.; Baaziz, H.; Ghellab, T.; Charifi, Z.; Soyalp, F.
The present study explores the structural, optoelectronic, and thermoelectric properties of potassium tin halide vacancy-ordered double perovskites K2SnX6 (X = Cl, Br, and I) in their stable monoclinic phase. Our study uses first-principles calculations based on density functional theory (DFT). Electronic band structures reveal direct band gaps for K2SnCl6 and K2SnBr6, while K2SnI6 exhibits an indirect band gap. Theoretical computations utilising the modified Becke-Johnson potential (mBJ-GGA) demonstrate that the optical band gaps of K2SnCl6, K2SnBr6, and K2SnI6 decrease in the following order: 2.581 eV, 1.707 eV, and 4.126 eV, respectively. These values render the materials suitable for photovoltaic applications. Analysis of dielectric functions, absorption coefficients, and refractive indices demonstrates their potential as light-absorbing materials. We evaluate the thermoelectric properties, including electronic and lattice thermal conductivities, Seebeck coefficients, and power factors, which lead to favorable thermoelectric performance. The maximum figure of merit (ZT) values of 0.58, 0.69, and 0.50 are achieved for K2SnCl6, K2SnBr6, and K2SnI6, respectively, at 500 K. These findings highlight the potential of these materials for applications in solar cells and thermoelectric devices, emphasising their effectiveness at elevated temperatures. © 2024 IOP Publishing Ltd.
First Principles Calculation of the Structural, Electronic, Optical and Elastic Properties of the Cubic Alxga1-Xsb Ternary Alloy
(Elsevier, 2021) Moussa, R.; Abdiche, A.; Khenata, R.; Soyalp, F.
The aim of this paper is to investigate the structural, electronic, optical and elastic properties of the cubic AlxGa1-xSb ternary alloy with their related binary compounds GaSb and AlSb. The calculations are performed within density functional theory (DFT) using full-potential linearized augmented plane wave (FP-LAPW) method as implemented in Wien2k package. It is found that the lattice parameter of the AlxGa1-xSb ternary alloy shown a non-linear variation with the Aluminum (Al) mole fraction. Beside, the band gap variations with the composition of the ternary alloy exhibit also a small deviation from the Vegard's law, and the obtained results confirm the semiconducting character of the studied materials. Furthermore, the optical properties of the materials are calculated and compared with the theoretical models and with the experimental data found in the literature where a good agreement is observed. The elastic properties of the studied alloys are also determined in this study and they are compared with other works available in the literature.
First Principles Linear Response Calculations of Phonons for Scp and Scas
(Pergamon-elsevier Science Ltd, 2008) Ugur, S.; Soyalp, F.
An ab initio pseudopotential method is used to investigate the Structural and phonon Properties of SO and ScAs in the B1(NaCl) structure. The calculated lattice constants, static bulk modulus and first-order pressure derivative of the bulk modulus are reported in B I structure and compared with previous calculations. A linear-response approach to the density-functional theory is used to derive the phonon frequencies and density of states. The phonon dispersion curves for the two materials are compared. (c) 2008 Elsevier Ltd. All rights reserved.
First Principles Study of Hydrogen Storage Material Nabh4 and Lialh4 Compounds: Electronic Structure and Optical Properties
(Iop Publishing Ltd, 2016) Ghellab, T.; Charifi, Z.; Baaziz, H.; Ugur, S.; Ugur, G.; Soyalp, F.
A comprehensive study of structure, phase stability, optical and electronic properties of LiAlH4 and NaBH4 light-metal hydrides is presented. The calculations are carried out. within density functional theory using the full potential linear augmented plane wave method. The exchange-correlation potential is treated within the local density approximation. and the generalized gradient approximation (GGA) to calculate the total energy. Furthermore, the Engel-Vosko GGA. approach is employed to compute. electronic and optical properties such as reflectivity spectra. The phases a, beta and gamma of LiAlH4 and NaBH4 hydrides are investigated, the phase transition from the beta to the. high-pressure gamma phase is determined for NaBH4. and is accompanied by a 1% volume decrease. For LiAlH4, no phase transition is detected. The materials under consideration are classified as wide band gap compounds. From the analysis of the structures at different phases, it is deduced that the hydrides show strong covalent interaction between B (Al) and H in the [BH4](-) ([AlH4](-)) anions and ionic bonding character between [BH4](-) and Na+ for NaBH4, and [AlH4](-) and Li+ for LiAlH4. The complex dielectric function, absorption coefficient and the reflectivity spectra are also computed and analyzed in different phases.
The First Principles Study on Las Compound
(Elsevier, 2008) Soyalp, F.
The structural, electronic and dynamical properties of LaS compound in NaG (B1) and CsCl (B2) structures are studied by performing ab initio calculations within the generalized gradient approximation (GGA). The calculated lattice constants, static bulk modulus, first-order pressure derivative of the bulk modulus and band structures are reported in both NaCl and CsCl structures and compared with theoretical and available experimental results. The transition pressure for the B1 type to B2 type structure is calculated to be about 20.8 GPa. A linear-response approach to density functional theory is used to derive phonon dispersion curves and density of states. The calculated phonon spectra are in good agreement with available experimental results. A detailed discussion of atomic displacement pattern is also presented. (C) 2007 Elsevier B.V. All rights reserved.
First-Principle Study of the Structural, Electronic, and Optical Properties of Cubic Innxp1-X Ternary Alloys Under Hydrostatic Pressure
(Walter de Gruyter Gmbh, 2016) Hattabi, I.; Abdiche, A.; Moussa, R.; Riane, R.; Hadji, K.; Soyalp, F.; Khenata, R.
In this article, we present results of the first-principle study of the structural, electronic, and optical properties of the InN, InP binary compounds and their related ternary alloy InNxP1-x in the zinc-blend (ZB) phase within a nonrelativistic full potential linearised augmented plan wave (FP-LAPW) method using Wien2k code based on the density functional theory (DFT). Different approximations of exchange-correlation energy were used for the calculation of the lattice constant, bulk modulus, and first-order pressure derivative of the bulk modulus. Whereas the lattice constant decreases with increasing nitride composition x. Our results present a good agreement with theoretical and experimental data. The electronic band structures calculated using Tran-Blaha-modified Becke-Johnson (TB-mBJ) approach present a direct band gap semiconductor character for InNxP1-x compounds at different x values. The electronic properties were also calculated under hydrostatic pressure for (P = 0.00, 5.00, 10.0, 15.0, 20.0, 25.0 GPa) where it is found that the InP compound change from direct to indirect band gap at the pressure P = 7.80 GPa. Furthermore, the pressure effect on the dielectric function and the refractive index was carried out. Results obtained in our calculations present a good agreement with available theoretical reports and experimental data.
First-Principles Investigation of Structural, Electronic and Dynamical Properties in Scausn Alloy
(Elsevier Science Bv, 2007) Soyalp, F.; Ugur, S.; Ugur, G.
A theoretical study of structural, electronic and dynamical properties of the ScAuSn is presented by using the density functional theory within the generalized gradient approximation (GGA). The lattice constant of this material is found to be 6.501 angstrom, which compares very well with the experimental value of 6.419 angstrom. We have carried out band structure and density of states calculations for ScAuSn. Then, a linear-response approach to the density-functional theory is used to derive the phonon frequencies and density of states. (c) 2007 Elsevier B.V. All rights reserved.
First-Principles Study of B2-Like Intermetallics Lamg and Ymg
(Elsevier Sci Ltd, 2012) Ugur, S.; Ugur, G.; Soyalp, F.; Ellialtioglu, M. R.
The first-principles total energy calculations using generalized gradient approximation (GGA) and the plane wave pseudopotential method were employed to investigate the structural, elastic, electronic, and phonon properties of LaMg and YMg in the B2 (CsCl) phase. The elastic constants were derived from the stress strain relation. Lattice parameters, bulk modulus and its pressure derivative, and second order elastic constants were found to be in excellent agreement with the previous experimental and theoretical data. We also carried out the electronic band structure and the density of states (DOS) calculations for LaMg and YMg. Moreover, a linear-response approach to the density functional theory was used to derive the phonon frequencies and the phonon density of states. The temperature variation of specific heats in the range of 0-400 K were obtained using the quasi-harmonic model. (C) 2011 Elsevier Ltd. All rights reserved.
The First-Principles Study of Lase and Late in B1 and B2 Structures
(Elsevier Science Bv, 2009) Soyalp, F.
The structural, electronic and dynamical properties of LaSe and LaTe compounds in NaCl(B1) and CsCl(B2) structures are studied by performing ab initio calculations within the generalized gradient approximation (GGA). Bulk properties including lattice constants, static bulk modulus, first-order pressure derivative of the bulk modulus, cohesive energies and first-order phase transitions are reported and compared with available experimental and other theoretical results. The electronic band structure is also presented for these materials. For the first time, the electronic structure results are used, within the implementation of linear-response technique, for calculations of phonon properties. A detailed discussion of atomic displacement pattern for LaTe in B1 structure is also presented. The phonon dispersion curves for two materials are compared and contrasted. (C) 2008 Elsevier B.V. All rights reserved.