COORDINATION BEHAVIOR OF THE CORE AND VALENCE LEVELS OF LOW-COORDINATED OXYGEN IONS ON THE SURFACE OF MAGNESIUM-OXIDE

For low-coordinated (N = 2, 3, 4, 5) oxygen ions on the surface and in the bulk of magnesium oxide, the behavior of the core O1s- and valenc e O2s-, O2p-levels is considered. The MgO610-, OMg610+ Mg13O142-, O13M g142+, Mg4O76-, and OMg22+ clusters are calculated by the SCF-X alpha- SW method. The binding energies of oxygen 1s-, 2s-, and 2p-states decr ease with coordination. This coordination dependence is explained by t he greater change of the Madelung potential as compared to variations of the purely electronic terms of the binding energies of oxygen ions. The dependence of oxygen atomic charges and relaxation energies on co ordination is also discussed.