Theoretical study of structural, electronic and optical properties of BaxPb1−xS, BaxPb1−xSe and BaxPb1−xTe ternary alloys using FP-LAPW approach

Abstract

The structural, electronic and optical properties of BaxPb1−xS, BaxPb1−xSe and BaxPb1−xTe alloys for 0 ≤ x ≤ 1 in their rock-salt (B1) crystallographic phase have been calculated using the full-potential linearized augmented plane wave (FP-LAPW) method under the framework of density functional theory (DFT). Using the Wu-Cohen generalized-gradient approximation (WC-GGA) parameterization scheme, ground-state structural parameters such as equilibrium lattice constants, bulk modulus and its pressure derivatives are calculated and deviations of the lattice constants from Vegard's law and the bulk modulus from linear concentration dependence have been observed for the alloys. Electronic band structures and density of states have been calculated using Tran-Blaha modified Becke-Johnson (TB-mBJ) parameterization scheme to study the electronic properties of the binary compounds and their ternary alloys. In addition, Engel-Vosko generalized gradient approximation (EV-GGA) and WC-GGA induced energy band gaps have also been calculated for comparison. Using the approach of Zunger and co-workers, the microscopic origins of band gap bowing have been discussed in term of volume deformation, charge exchange and structural relaxation. Optical properties of the binary compounds and their ternary alloys have been calculated in terms of their respective dielectric function, refractive index, reflectivity and optical conductivity. Few calculated results are compared with available experimental and other theoretical data.