Laboratory for Developing New Materials and their Characterization

Sétif, Algeria

Laboratory for Developing New Materials and their Characterization

Sétif, Algeria

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Hichour M.,University of Mascara | Khenata R.,University of Mascara | Khenata R.,King Saud University | Rached D.,University Djilali Liabes | And 5 more authors.
Physica B: Condensed Matter | Year: 2010

Structural, electronic, elastic and optical properties of the cubic-antiperovskite-type ANSr3, with A=As, Sb and Bi, are studied under pressure effect using the full-relativistic version of the full-potential augmented plane wave plus local orbitals method (FP-APW+lo). The exchange-correlation potential is treated by the generalized gradient approximation within the scheme of Perdew, Burke and Ernzerhof (GGA-PBE). Also we have used Engel and Vosko GGA formalism (GGA-EV) to improve the band gap results. The calculated bulk properties, including lattice constants, bulk moduli and their pressure derivatives are in reasonable agreement with the available data. The elastic constants Cij and their pressure dependences are calculated using the total energy-strain technique. The shear modulus, Young's modulus, Poisson's ratio and Lame's coefficients are estimated in the framework of the Voigt-Reuss-Hill approximation for ideal polycrystalline ANSr3 aggregates. The Debye temperature is estimated from the average sound velocity. Energy band structures show that the investigated materials are direct energy band gap semiconductors. Analysis of the density of states and charge density distribution shows that the bonding is a mixture of covalent and ionic character. For the first time, the real and imaginary parts of the dielectric function ε(ω), the refractive index n(ω), the reflectivity R(ω) and the energy loss function L(ω) are calculated for radiation up to 18 eV. © 2010 Elsevier B.V. All rights reserved.


Haddadi K.,Laboratory for Developing New Materials and their Characterization | Bouhemadou A.,Laboratory for Developing New Materials and their Characterization | Bouhemadou A.,King Saud University | Louail L.,Laboratory for Developing New Materials and their Characterization
Solid State Communications | Year: 2010

We have investigated the structural, elastic and electronic properties of the anti-perovskite TlNCa3 using ab initio calculations within the generalized gradient approximation and the local density approximation for the exchange-correlation potential. The lattice constant, bulk modulus, elastic constants and their pressure dependence, energy band structures, density of states and charge density distribution are calculated and analyzed in comparison with the available experimental and theoretical data. The bulk modulus, shear modulus, Young's modulus, Poisson's ratio, Lamé's coefficients, average sound velocity and Debye temperature are numerically estimated for ideal polycrystalline TlNCa3 aggregates in the framework of the Voigt-Reuss-Hill approximation. This is the first theoretical prediction of the elastic constants and their related properties for TlNCa3 that requires experimental confirmation. © 2010 Elsevier Ltd. All rights reserved.


Bouhemadou A.,Laboratory for Developing New Materials and their Characterization | Bouhemadou A.,King Saud University | Haddadi K.,Laboratory for Developing New Materials and their Characterization
Solid State Sciences | Year: 2010

First-principles calculations are performed to investigate the structural, elastic, electronic and thermal properties of the cubic perovskite-type BaSnO3. The ground-state properties are in agreement with experimental data. The independent elastic constants, C11, C12 and C44, are calculated from direct computation of stresses generated by small strains. A linear pressure dependence of the elastic stiffnesses is found. From the theoretical elastic constants, we have computed the elastic wave velocities along [100], [110] and [111] directions. The shear modulus, Young's modulus, Poisson's ratio, Lamé's coefficients, average sound velocity and Debye temperature are estimated in the framework of the Voigt-Reuss-Hill approximation for ideal polycrystalline BaSnO3 aggregate. Using the sX-LDA for the exchange-correlation potential, the calculated indirect fundamental band gap value is in very good agreement with the measured one. The analysis of the site-projected l-decomposed density of states, charge transfer and charge density shows that the bonding is of ionic nature. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the temperature effect on the lattice constant, bulk modulus, thermal expansion coefficient, heat capacity and Debye temperature is calculated. © 2010 Elsevier Masson SAS. All rights reserved.

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