Browsing by Author "Ocak, H. Y."

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Structural, Elastic, Electronic and Optical Properties of Cu3tmse4 (Tm = V, Nb and Ta) Sulvanite Compounds Via First-Principles Calculations
(Amer Scientific Publishers, 2013) Bougherara, K.; Litimein, F.; Khenata, R.; Ucgun, E.; Ocak, H. Y.; Ugur, S.; Bin Omran, S.
The structural and optoelectronic properties of the cubic Cu3TMSe4 (TM = V, Nb and Ta) sulvanite compounds have been calculated using a full-potential augmented plane wave plus local orbitals (FP-APW + lo) method within the density functional theory. The exchange-correlation potential was treated with the generalized gradient approximation of Wu and Cohen (WC-GGA) to calculate the total energy. Moreover, the Engel-Vosko generalized gradient approximation (EV-GGA) and the modified Becke-Johnson potential (TB-mBJ) were also applied for the electronic and optical properties. The ground state properties, including, lattice constants, bulk modulus are in reasonable agreement with the available experimental and theoretical data. The elastic constants C-ij are computed using the total energy variation versus strain technique. The polycrystalline elastic moduli, namely; shear modulus, Young's modulus, Poisson's ratio and anisotropic factor were derived from the obtained single-crystal elastic constants. As a result, brittleness behaviour of these compounds is interpreted via the calculated elastic constants C-ij. The calculations of the electronic band structure show that these compounds have an indirect energy band gap (R-X) and the TB-mBJ approximation yields larger fundamental band gaps compared to those of WC-GGA and EV-GGA. The dielectric function, refractive index, extinction coefficient, reflectivity, and energy loss function were calculated for radiation up to 45 eV.
Theoretical Prediction of the Fundamental Properties for the Ternary Li2pth6 and Na2pth6
(Academic Press inc Elsevier Science, 2012) Ghebouli, M. A.; Choutri, H.; Bouarissa, N.; Ghebouli, B.; Bouhemadou, A.; Soyalp, F.; Ocak, H. Y.
Li2PtH6 and Na2PtH6 are good candidate for hydrogen storage. The structural, elastic, electronic and optical properties of Li2PtH6 and Na2PtH6 compounds have been investigated using pseudo-potential plane-wave method based on the density functional theory. Computed lattice constant and H atom positional parameter at equilibrium agree well with the available experimental data. A quadratic pressure dependence of the elastic stiffness is found. A set of isotropic elastic parameters and related properties, namely bulk and shear moduli, Young's modulus, Poisson's ratio, average sound velocity and Debye temperature are numerically estimated in the framework of the Voigt-Reuss-Hill approximation for Li2PtH6 and Na2PtH6 polycrystalline aggregate. The analyses of the band structure indicates that Li2PtH6 and Na2PtH6 are indirect gap semiconductors. The static dielectric constant and static refractive index are inversely proportional to the fundamental gap. (C) 2012 Elsevier Inc. All rights reserved.