First-principles study of electronic structure of Calvertite and effect of substitution by Si and Sn

Abstract

The electronic structures of Cu10XS8 (with X = Ge, Si or Sn) have been investigated using first-principles linearized augmented plane wave method based on density functional theory. The total energy is computed for Calvertite mineral, and the modeled Cu10SiS8 and Cu10SnS8 crystals. The computed total energy is coupled with the Birch-Murnaghan equation of state to report the equilibrium lattice constant and the bulk modulus of the three materials. A few thermal properties such as thermal expansion coefficient, Grϋneisen parameter, specific heat, Debye temperature are also calculated. We present a comparative study of electronic and structural properties of Calvertite mineral with the materials modeled by replacing the Ge with Si or Sn. Electronic band structures of the three crystals highlight metallic properties. The detailed analysis of the Fermi surfaces of all crystals is presented.