Electronic Energy-Band Structure of SnS2and SnSe2

The local-empirical-pseudopotential method is used to calculate the electronic band structure of Sn${\mathrm{S}}_2$ and Sn${\mathrm{Se}}_2$. The pseudopotential form factors for the constituent elements Sn, S, and Se are determined from previous pseudopotential calculations for other crystals. Slight adjustments were made to give the correct fundamental gaps. A group-theoretical study of the symmetry properties of these crystals is included. The imaginary part of the dielectric function, ${\epsilon }_2\left(\omega \right)$, is calculated for Sn${\mathrm{S}}_2$. Some comparison is made between the theory and the existing experimental data.