First-principles calculations of optical absorption spectra of atoms in the vacuum and crystals

Starting from the GW approximation (GWA) beyond the density functional theory and taking into account the excitonic effect, we have determined optical properties of isolated Zn atom and also Cu impurity atom in NaCl crystal. In the representation of single electron wave functions, we have used the all-electron mixed basis approach in which both plane waves and atomic orbitals are used as a basis set. The resulting quasipartile energies and optical absorption spectra are compared with available experimental data.