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 in MgO crystals: F⁺ and F centres (one and two electrons trapped by 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, 2.72 eV and 3.13 eV, respectively).