The Electronic Structure of the Alkaline-Earth Oxides. V. Peculiarities of the Hole-Trapping in NaF and MgO^†

Calculations are made for clusters simulating the V_k-center in NaF and a hypothetic self-trapped hole in MgO within the embedded cluster approach. The “non-ionic” charge configuration of MgO, described earlier, is analysed as a possible cause of the absence of the hole self-trapping manifestations in the oxide according to the mechanism known for NaF. Due to the delocalization of oxygen 2p-states the hole orbital is oriented, in contrast to NaF, perpendicularly to the 2-anion quasi-molecule axis, while the hole state itself lies close to the top of the potential barrier bonding this state.