Energy band structure and optical properties of Sb2S3 and SbI3 crystals : First principles calculations

In this dissertation, the electronic band structures, density of states (DOS) and optical properties of and -type binary compounds, and , are investigated by using the density functional theory (DFT) and ab-initio pseudopotential method within the local density approximation (LDA). The obtained electronic band structure shows that and crystals have an indirect forbidden band gap of 0.7278 eV and 1.7141 eV, respectively and that smallest forbidden direct band gap (0.8333 eV and 1.740 eV) are at the and high symmetry point of the Brillouin zone, respectively. The linear photon-energy dependent dielectric functions and some optical properties such as the absorption coefficient, extinction coefficient, refractive index, energy-loss function and reflectivity are calculated for both crystals. Moreover, some important optical parameters such as the effective number of valance electrons and the effective optical dielectric constant are calculated. It is found that the method used estimated the properties of these crystals quite well.