The atomic and electronic structure of H- ions substituting for O2- ions in regular sites in MgO crystals are calculated using an ab initio Hartree-Fock (HF) cluster approach and its semiempirical version, intermediate neglect of the differential overlap. The theoretical optical absorption energy is predicted to be 10 eV, which is supported by analysis of experimental data for the H- centers in a series of ionic crystals. The HF simulations of H- ion diffusion via direct interstitial hops along the [100] axis predict an activation energy of about 3 eV.
Phys. Rev. B 59, 1885 - 1890 (1999)

Semi-empirical quantum chemical simulations of 125-atom clusters have been undertaken to obtain the self-consistent atomic and electronic structure of the two basic electron defects in MgO crystals — F+ and F centers (one and two electrons trapped by an O vacancy). The calculated absorption and luminescence energies agree well with the experimental data, the excited states of both defects are found to be essentially delocalized over nearest-neighbour cations. The mechanism of the F+ → F photoconversion is discussed.
Computational Materials Science, Volume 5, 1996, Pages 298-306