Quantum chemical simulations of the optical properties and diffusion of electron centres in MgO crystals

Semiempirical quantum chemical simulations have been undertaken to obtain the self-consistent atomic and electronic structure of the two basic electron defects is in MgO crystals: F+ and F centres (one and two electrons trapped bq an O vacancy, V-a). The calculated absorption and luminescence energies agree well with the experimental data; the excited states of both defects are found to be essentially delocalised over nearest-neighbour cations. The activation energy for diffusion is found to increase monotonically in a series V-a --> F+ --> F centre (2.50 eV, 2.73 eV and 3.13 eV, respectively).