Electronic band structure of AgCd2GaS4: theory and experiment

Abstract

We report theoretical calculations of the band structure ofAgCd2GaS4 using the full-potential linear augmented plane wave method and experimentalmeasurements of the valence band x-ray photoelectron spectroscopy. We find that thevalence band maximum and the conduction band minimum are located at theΓ point of the Brillouin zone resulting in a direct energy gap of 1.0 eV compared to ourmeasured experimental value of 2.15 eV. Our analysis of the partial density of states showsthat there is a weak covalent interaction between Ag and Ga atoms and between Ag andCd atoms, and a substantial covalent interaction between Ag and S atoms. Thus theGa–Ag and Cd–Ag bonds are basically of ionic character, and Ag–S bonds are of covalentcharacter. The theoretical results of the density of states are in agreement with the valenceband x-ray photoelectron spectroscopy measurements with respect to spectral peakpositions. We have analyzed the calculated density of states and find a strong/weakhybridization between the Ag, Cd, Ga and S states in the valence and conduction bands.