Optical properties of BiSBr and BiSeBr crystals

Optical properties of BiSBr and BiSeBr crystals were investigated by the full potential linearized augmented plane wave (FP-LAPW) method with density-functional theory (DFT). The complex dielectric function and optical constants, such as optical absorption coefficient, refractive index, extinction coefficient, energy-loss spectrum and reflectivity, were calculated and compared in the energy range of 0–30 eV. Origin of anisotropic behavior of optical spectra was also discussed. The plasmon energy ℏ ω p was estimated to be 18 eV for BiSeBr and 20 eV for BiSBr crystal. ► Optical properties of BiSBr and BiSeBr crystals were investigated by FP-LAPW method. ► Origin of anisotropic behavior of optical spectra was discussed. ► The plasmon energy was estimated in three different ways.