Search

In this study, we present our predicted results related to the structural, electronic, and optical properties of Ga(x)In(1-x)AsyN(1-y) quaternary alloys while assessing the associated zinc blende binary and ternary compounds. All calculations are performed by employing the full-potential linearized augmented plane wave plus local orbital method (FP-L(APW + lo)) based on density functional theory (DFT) and implemented in the WIEN2k computational package for crystalline materials. The exchange-correlation energy and potential functional are treated by the local density approximation (LDA) parameterized by Perdew-Wang (PW) and the PBE functional for solids, i.e., PBEsol-GGA, for the calculations of structural parameters, while the Tran-Blaha Becke-Johnson (TB-mBJ) potential approximation combined with PBE-GGA is applied for band structure calculation. The composition-dependent results of the lattice parameters, bulk modulus, and bandgap energy are also studied by performing a quadratic fit, where nonlinear variations in the results are observed. One can note that the bandgap energies are direct for all considered compositions (x, y). Moreover, the dielectric behavior, refractive index, and loss energy are predicted in the context of the optical properties, and the variation in the composition slightly affects the optical stability of the studied alloys. We have also carried out predictions of the thermodynamic properties such as the lattice parameter a(P, T), the Debye temperature theta(D), the heat capacity C-v, and the entropy S using the GIBBS program. To the best of our knowledge, this work represents the first theoretical study on these quaternary alloys and awaits experimental confirmation.

We investigated the structural stability as well as the mechanical, electronic and magnetic properties of the Full-Heusler alloy CoNiMnSi using the full-potential linearized augmented plane wave (FP-LAPW) method. Two generalized gradient approximations (GGA and GGA + U) were used to treat the exchange-correlation energy functional. The ground state properties of CoNiMnSi including the lattice parameter and bulk modulus were calculated. The elastic constants (Cij) and their related elastic moduli as well as the thermodynamic properties for CoNiMnSi have been calculated for the first time. The existence of half-metallic ferromagnetism (HM-FM) in this material is apparent from its band structure. Our results classify CoNiMnSi as a new HM-FM material with high spin polarization suitable for spintronic applications.

We have studied the structural, optical, electronic and thermoelectric properties of the CaCd2X2 (X = P, As) compounds by using the full-potential augmented plane wave plus local orbitals method (FP-APW + lo). The exchange-correlation potential was treated using both the gradient generalized approximation (WC-GGA) and local density approximation (LDA). The estimated structural parameters, including the lattice parameters and internal coordinates agree well with the available experimental data. Our computed band structure shows that both studied compounds are semiconductors, with direct band gaps (Γ-Γ) of approximately 1.78 eV and 1.2 eV for CaCd2P2 and CaCd2As2, respectively, using GGA-TB-mBJ approach. The calculated optical spectra reveal a strong response of these materials in the energy range between the visible light and extreme UV regions, making them a good candidate for optoelectronic devices. Thermoelectric parameters, such as thermal conductivity, electrical conductivity, Seebeck coefficient, power factor and figure of merit were calculated. We note that both the CaCd2P2 and CaCd2As2 compounds show promising thermoelectric properties.

In this work, we have theoretically investigated the band structure of antiperovskite chromium-based carbides and nitrides Cr 3 PX (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 Cr 3 PC and Cr 3 PN compounds at (001) plane is higher than the (100) and (010) planes. Moreover, the Cr 3 PX compounds are expected to be hard materials with ductile nature. In addition, we have found that the FM ground state of herein materials Cr 3 PC and Cr 3 PN are energetically favorable with low magnetic moments of about 2.27 and 2.94 μ B , 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 Cr 3 PC and Cr 3 PN compounds.

International audience; The Wang-Landau Monte Carlo algorithm is implemented within an effective Hamiltonian approach and applied to BaTiO 3 bulk. The density of states obtained by this approach allows a highly accurate and straightforward calculation of various thermodynamic properties, including phase transition temperatures, as well as polarization, dielectric susceptibility, specific heat, and electrocaloric coefficient at any temperature. This approach yields rather smooth data even near phase transitions and provides direct access to entropy and free energy, which allow us to compute properties that are typically unaccessible by atomistic simulations. Examples of such latter properties are the nature (i.e., first order versus second order) of the phase transitions for different supercell sizes and the thermodynamic limit of the Curie temperature and latent heat.

We report a systematic study of the structural, electronic, optical and elastic properties of the ternary ruthenium-based hydrides A(2)RuH(6) (A=Mg, Ca, Sr and Ba) within two complementary first-principles approaches. We describe the properties of the A(2)RuH(6) systems looking for trends on different properties as a function of the A sublattice. Our results are in agreement with experimental ones when the latter are available. In particular, our theoretical lattice parameters obtained using the GGA-PBEsol to include the exchange-correlation functional are in good agreement with experiment. Analysis of the calculated electronic band structure diagrams suggests that these hydrides are wide nearly direct band semiconductors, with a very slight deviation from the ideal direct-band gap behaviour and they are expected to have a poor hole-type electrical conductivity. The TB-mBJ potential has been used to correct the deficiency of the standard GGA for predicting the optoelectronic properties. The calculated TB-mBJ fundamental band gaps are about 3.53, 3.11, 2.99 and 2.68eV for Mg2RuH6, Ca2RuH6, Sr2RuH6 and Ba2RuH6, respectively. Calculated density of states spectra demonstrates that the topmost valence bands consist of d orbitals of the Ru atoms, classifying these materials as d-type hydrides. Analysis of charge density maps tells that these systems can be classified as mixed ionic-covalent bonding materials. Optical spectra in a wide energy range from 0 to 30eV have been provided and the origin of the observed peaks and structures has been assigned. Optical spectra in the visible range of solar spectrum suggest these hydrides for use as antireflection coatings. The single-crystal and polycrystalline elastic moduli and their related properties have been numerically estimated and analysed for the first time.

The full potential linearized augmented plane wave method within the framework of density functional theory (DFT) is employed to investigate the structural, magnetic, electronic and optical properties of Ti -doped ZnTe and CdTe in the zinc blende phase. In this approach the local spin density approximation (LSDA) is used for the exchange-correlation (XC) potential. Results are provided for the lattice constant, bulk modulus, pressure derivative, magnetic moment, band structure, density of states and refractive indices. Our results are compared with other theoretical works and good agreement is shown.

WOS: 000330643000005, Structural, electronic, elastic and thermodynamic properties of Rh3X ( X = Zr, Nb, Ta) intermetallic compounds are investigated in the framework of density functional theory (DFT). The exchange-correlation (XC) potential is treated with the generalized gradient approximation (GGA) and local density approximation (LDA). The computed ground state properties agree well with the available theoretical and experimental values. The elastic constants are obtained by calculating the total energy versus volume conserving strains using Mehl model. The electronic and bonding properties are discussed from the calculations of band structures (BSs), densities of states and electron charge densities. The volume and bulk modulus at high pressure and temperature are investigated. Additionally, thermodynamic properties such as the heat capacity, thermal expansion and Debye temperature at high pressures and temperatures are also analyzed., Deanship of Scientific Research at King Saud University [RPG-VPP-088], The authors R. K., A. B., Z. A. A. and S. B. O acknowledge the financial support by the Deanship of Scientific Research at King Saud University for funding the work through the research group project No. RPG-VPP-088. The author A. Sayede thanks the Centre de Ressources Informatiques (CRI) of the University of Lille for providing the computational facilities.

The full potential linearized augmented plane wave method within the framework of density functional theory is employed to investigate the structural, thermodynamic and elastic properties of the yttrium chalcogenides (YX: X=S, Se, and Te) in their low-pressure phase ( F m 3 ¯ m ) and high-pressure phase ( P m 3 ¯ m ). The exchange-correlation potential is treated with the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA-PBE). Temperature dependence of the volume and both adiabatic and isothermal bulk moduli is predicted for a temperature range from 0 to 1200 K for the both phases of the herein considered materials. Furthermore, we have analyzed the thermodynamic properties such as the heat capacities, CV and CP, thermal expansion, α, and Debye temperature, ΘD, under variable pressure and temperature. We have calculated the isothermal elastic constants CijT of the YX monochalcogenides in both NaCl-B1 and CsCl-B2 phases at zero pressure and a temperature range 0 − 1200 K . The results show that rare earth yttrium monochalcogenides are mechanically stable at high temperature. The elastic anisotropy of all studied materials in the two phases has been studied using three different methods.

Results of ab initio calculations of the lattice parameter, elastic constants and some thermodynamic parameters in a wide range of pressures and temperatures are reported for the ZnSc2S4 and CdSc2S4 cubic spinels. The calculated equilibrium lattice parameters are compared with available experimental data. Elastic constants and some related properties for single-crystal and polycrystalline have been calculated at zero pressure and zero temperature using the analysis of changes in calculated stresses resulting from changes in strain. Evolution of the elastic constant with pressure and temperature is predicted. From the ab initio calculated total energy versus volume and using the quasi-harmonic Debye model, in which the phononic effects are taken into account, the evolution of some thermodynamic parameters with temperature and pressure is computed. This is the first quantitative theoretical prediction of the reported properties and it still awaits experimental confirmation. (C) 2013 Elsevier B. V. All rights reserved.

We report a detailed study of the compositional dependence of the structural, elastic, electronic and dynamical properties of the In1 -x-yAlxGayP quaternary alloys matched to AlP using pseudo-potential plane-wave method based on the density functional theory. The reliability and accuracy of the predicted physical properties mentioned above for In1-x-yAlxGayP/AlP are tested by comparing the calculated lattice constant, elastic constants and phonon dispersion curves for the binary AlP with the available experimental and theoretical data in the literature. © 2012 Elsevier Ltd. All rights reserved., Deanship of Scientific Research, King Saud University: RGP-VPP-088, The authors (A. Bouhemadou and S. Bin-Omran) extend their appreciation to the Deanship of Scientific Research at King Saud University for funding the work through the research group project No RGP-VPP-088.

Density functional theory (DFT) is performed to study the structural, electronic and optical properties of cubic fluoroperovskite AMF3( 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 ε(ω), the refractive index n(ω) and the extinction coefficient k(ω)) were calculated for radiation up to 40.0 eV.

Structural, elastic, electronic and magnetic properties of Mn3ZnC and Mn3GeC are investigated via ab initio calculations. Total energy calculations show that the ferromagnetic state is energetically more stable than the non-magnetic state at equilibrium volume. No found imaginary phonon frequency in the whole Brillouin zone for the two compounds supports their dynamical stability. The elastic parameters are predicted. The electrical conductivity is assured by the Mn-d electrons. The total moment comes principally from the transition metal Mn in both compounds. The magnetic moment of the Mn atom decrease considerably when the Zn atom is substituted by the Ge one. (C) 2012 Elsevier B.V. All rights reserved.

Density functional-based method has been used to investigate the systematic trends for structural parameters, elastic stiffness, lattice dynamics and thermal properties of cubic perovskite-type RBRh3 depending on the type of R atoms (R are Sc, Y, La and Lu). The structural parameters, single-crystal elastic constants, directional elastic wave velocities and their pressure dependence are calculated and analyzed in comparison with the available experimental and theoretical data. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young's modulus, Poisson's ratio, Lame's coefficients, average sound velocity. Debye temperature and thermal conductivity are predicted in the frame work of the Voigt-Reuss-Hill approximation for the polycrystalline RBRh3. The correlation between the mechanical properties and electronic structures has been discussed. Using the density-functional perturbation theory (DFPT), the phonon properties of RBRh3 (R = Sc, Y and La) are investigated for the first time. (C) 2011 Elsevier B.V. All rights reserved.