First Principles Study Of Electronic Band Structure And Optical Properties Of Sb2S3 And Sb2Se3 Crystals

The description of electronic band structures and optical properties of AV2BVI3 type binary compounds, Sb2S3 and Sb2Se3, are investigated using the density functional theory under the local density approximation by using SIESTA code. The obtained electronic band structure shows that Sb2S3 and Sb2Se3crystals have an indirect forbidden gap of 0.62 eV and 0.7278 eV, respectively and that smallest direct band gap (0.83 eV and 0.71 eV) are at the Γ and X high symmetry point of the Brillioin zone, respectively. We report calculations of the linear photon-energy dependent dielectric functions and some optical functions as absorption and extinction coefficients, refractive index, energy-loss function and reflectivity. Moreover, some important optical parameters such as the effective number of valence electrons and the effective optical dielectric constant are calculated, too. We find the satisfactory agreement with the available experimental data.