Ab initio and semiempirical calculations of H- centers in MgO crystals

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-Fo ck (HF) cluster approach and its semiempirical version, intermediate neglec t 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. [S0163-1829(99)05303-5].