Contributions to the energy of a crystal which contained anion vacancies, and F+ and F centers, were calculated by using various approximations to the wave function that described the ground state of a defect. Molecular statics methods were used which were modified so as to take account of interactions between a so-called distributed defect and a point lattice. It was shown that, when a defect electron was modelled as a point charge, and relaxation of the lattice was neglected, the energy gain which resulted from a transition from a pure vacancy to an F+ center and from a transition from an F+ center to a F center was equal to about 24eV. This value decreased by a factor of about 2.5 when lattice relaxation and a non point-like electron charge distribution were taken into account.

A.B.Sobolev, A.M.Varaksin: Fizika Tverdogo Tela, 1995, 37[5], 1337-41 (Physics of the Solid State, 1995, 37[5], 726-8)