Quaternary Cu2HgGeSe4 selenide: Its electronic and optical properties as elucidated from TB-mBJ band-structure calculations and XPS and XES measurements

Abstract

We report on band-structure calculations, within a density functional theory (DFT), of total and projected densities of states as well as experimental investigation of the electronic structure of Cu2HgGeSe4 using X-ray photoelectron spectroscopy (XPS) method. The present DFT calculations bring an excellent correspondence of the total density of states curve to the experimental XPS spectrum of valence electrons employing in the calculations modified Becke-Johnson (mBJ) functional in the type of Tran and Blaha (TB-mBJ) for exchange–correlation (XC) potential and, in addition, the spin–orbit coupling (SOC) effect and Hubbard correction parameter U (TB-mBJ + SOC + U technique). The basic optical constants are calculated within the TB-mBJ + SOC + U technique and they reveal a big perspective of using the Cu2HgGeSe4 compound in optoelectronic appliances.