Ab initio calculations of structural, electronic, and optical properties of Cu ₂HgSnSe ₄

The electronic structure of Cu ₂HgSnSe ₄ in stannite structure is studied by the first-principles calculations. This material is a direct band-gap compound. In addition, the dielectric function, absorption coefficient, reflectivity, and energy-loss function are studied using the density functional theory within the generalized gradient approximation. We discuss the optical transitions between the valence bands and the conduction bands in the spectra of the imaginary part of the dielectric function at length. High and wide optical absorption spectrum is obtained. There are several prominent peaks for Cu ₂HgSnSe ₄ in the reflectivity spectra. And a rapid decrease of reflectance corresponds to the prominent peak in the energy-loss spectrum.