Detailed DFT studies of the electronic structure and optical properties of KBaMSe3 (MÂ =Â As, Sb)

Bonding nature as well as the electronic band structure, electronic charge density and optical properties of KBaMSe3 (M = As, Sb) compounds have been calculated using a full-potential augmented plane wave (FP-LAPW) method within the density functional theory. The exchange-correlation potential was handled with LDA and PBE-GGA approximations. Moreover, the Engel-Vosko generalized gradient approximation (EV-GGA) and the modified Beck-Johnson potential (mBJ) were also applied to improve the electronic band structure calculations. The study of band structure shows that KBaAsSe3/KBaSbSe3 compounds have an indirect band gap of 2.08/2.10 eV which are in close agreement with the experimental data. The bonding nature has been studied as well using the electronic charge density (ECD) contour in the (1 0 1) crystallographic plane. It has been revealed that As/Sb-O atoms forms a strong covalent, while Ba-Se atoms form weak covalent bonding and the ionic bonding is mainly found between K and Ba atoms. Moreover, the complex dielectric function, absorption coefficient, refractive index, energy-loss spectrum and reflectivity have been estimated. From the reflectivity spectra, we found that KBaAsSe3 compound shows greater reflectivity than KBaSbSe3, which means that KBaAsSe3 compound can be used as shielding material in visible and also in ultra violet region.