The atomic and electronic structures of the irradiation-induced Frenkel defect, Oi0, in monocrystals were predicted by using a full-potential linear muffin-tin orbital method. A 16-atom super-cell was used to optimize the interstitial defect geometry. It was found that the most energetically favorable ground state Oi configuration was the (111) dumb-bell, centered at a normal O site. The face-centered and cube-centered configurations were higher in energy by 1.45 and 3.57eV, respectively. The (111) configuration was close in energy to the (110) configuration, and this permitted the dumb-bell to rotate easily on a lattice site. In all of these cases, the interstitial O atom attracted a considerable additional electron density from its nearest normal O2- ions. This made it close to the Oi- ion rather than a neutral atom.

Interstitial-Oxygen-Atom Diffusion in MgO. T.Brudevoll, E.A.Kotomin, N.E.Christensen: Physical Review B, 1996, 53[12], 7731-5