Abstract
Electronic structures of oxide surfaces are discussed based on the results of recent DV (Discrete-Variational) -Xα cluster calculations. Surface electronic structures of oxide crystals with mixed ionic and covalent attributes are achieved by the following : A) reduction of the Madelung potential compared to the bulk, B) strong field on the surface ionic site and the distortion of the ionic orbitals, C) the lack of orbital mixing between the surface ions and its nearest removed counter ions, and D) the reduction of the ionicity of surface ions and the enhanced covalency on the remaining bonds around it.
The localized electronic states associated with surface defects are clarified and their significance to surface chemical activity is discussed. The origin of the compensating charge of the polar surfaces is made clear and their peculiar electronic properties are studied.
