The change in the diffusion barrier for anion vacancies in polar crystals was calculated in the case where one electron (F centers) or two electrons (F′ centers) were captured. The lowest singlet and triplet states were considered for the two-electron system. It was shown that the capture of 2 electrons on the lowest metastable triplet state (which was possible under non-equilibrium conditions, for example, in the case of either exchange scattering of band electrons or thermal refilling of energy levels) led to a decrease in the diffusion barrier for the system. However, for the two-electron center in the lowest singlet state, the potential barrier to migration, as a rule, was higher than that for a vacancy without electrons. Calculations were carried out for Gaussian functions with the inclusion of the effects of inter-electron correlations and electron-phonon interactions.

Diffusion of One- and Two-Electron Vacancy Centers in Polar Crystals. N.I.Kashirina, V.D.Lakhno, V.V.Sychyov, M.K.Sheinkman: Physics of the Solid State, 2007, 49[5], 818-23