Influence of cationic substitution on the electronic structure of Cu7SiS5I and Ag7SiS5I compounds

Abstract

From the first principles in the framework of the density functional theory in LDA+U approximations, the band structure, the total and partial densities of electronic states, also the spatial distribution of the electron charge density of Cu7SiS5I and Ag7SiS5I superionic crystals had been calculated. The Cu→Ag substitution in the Cu7SiS5I and Ag7SiS5I compounds, along with an increase of the total width of the valence band, leads to a broadening and a change in the topology of the upper bond of the valence band, due to the pd-hybridization emerging between copper (silver) and sulfur atoms. It follows from the calculations of the band structure that the Cu7SiS5I compound is a direct-gap while Ag7SiS5I indirect semiconductor. Based on the data of the total and partial densities of electronic states, the contributions of atomic orbitals to crystalline ones are determined, also the data of the chemical bond formation in the crystals under discussion are obtained.