Ab initio calculations of the electronic and optical properties of germanium selenide.

We have performed an ab initio calculation of the germanium selenide electronic structure, adopting the LDA and GGA approximations for the exchange-correlation potential within the DFT. These calculations have been carried out with and without the inclusion of the spin-orbit interaction. The subtle changes it produces in the band structure, the density of states and the optical properties have been discussed. Also, we propose the s-Ge state contribution at the edge of the valence band as having an important role. Based on our electronic structure, we discuss germanium selenide experimental core spectra and optical properties. We found excellent agreement between our results and available experimental core spectra data, and our calculated optical functions of GeSe explain the origin of the optical transitions, comparing them satisfactorily against existing experimental data.