Within density functional theory based on the full potential-linearized augmented plane wave method, we carry out the first-principles calculation of the structural, electronic, and optical properties of the zinc blende quaternary alloy Zn 1−x BexSySe 1−y . The Perdew-Burke-Ernzerhof generalized gradient approximation based on the optimization of total energy and the Engel-Vosko generalized gradient approximation based on the optimization of the corresponding potential are used. Our investigation on the effect of the composition on lattice constants, bulk modulus, band gap, optical dielectric constant, and refractive index shows a non-linear dependence. The energy gap Eg(x, y) has been determined over the entire compositions x and y. In addition, the energy band gap of the technologically important quaternary alloy Zn 1−x BexSySe 1−y in conditions of being lattice matched to ZnS substrate has been investigated. It is noteworthy that the present work is the first theoretical study of the quaternary alloy of interest.

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Abstract:Structural, electronic and thermal properties of Zn 1− Mg S ternary alloys are studied by using the full potential-linearized augmented plane wave method (FP-LAPW) within the density functional theory (DFT). The Wu-Cohen generalized gradient approximation (WC-GGA) is used in this approach for the exchangecorrelation potential. Moreover, the modified Becke-Johnson approximation (mBJ) is adopted for band structure calculations. The dependence of the lattice constant, bulk modulus and band gap on the composition x showed that the first exhibits a small deviation from the Vegard's law, whereas, a marginal deviation of the second from linear concentration dependence (LCD). The bowing of the fundamental gap versus composition predicted by our calculations agrees well with the available theoretical data. The microscopic origins of the gap bowing are explained by using the approach of Zunger and co-workers. Thermal effects on some macroscopic properties of Zn 1− Mg S alloys are also investigated using the quasi-harmonic Debye model, in which the phononic effects are considered. As, this is the first quantitative theoretical prediction of the thermal properties of Zn 1− Mg S alloys, no other calculated results and furthermore no experimental studies are available for comparison. 64.75.-q, 65.40.-b, 71.20.-b, 81.90.+c PACS (2008):