First-principles study of electronic and optical properties of BaS, BaSe and BaTe

The optimized crystal structure, energy band structures, density of states (DOS) and optical properties of BaX (X=S, Se and Te) were investigated by the full potential linearized augmented plane wave plus local orbitals method (FP-LAPW+lo). The exchange-correlation potential was treated using the generalized gradient approximation (GGA). We have used also Engel and Vosko GGA (EV-GGA) formalism to improve the band gap results. The calculated results such as band gaps, dielectric constants and reflectivity spectra showed good agreement with the experimental data. The effect of the spin-orbit coupling (SOC) on the optical properties was also studied and found to be very small, especially in the low-energy region.