ATOMIC AND ELECTRONIC-STRUCTURE OF STEPS AND KINKS ON MGO(100) AND MGO(110)

The electronic and atomic structure of vicinal MgO surfaces are studie d using a quantum self-consistent method associated with a geometry op timization code. {10n}, {(n + 1)0n} and {n1n} surfaces, with periodic monoatomic steps separating {001} or {101} terraces, are considered. D iatomic steps along the (10n) orientation and periodic kinks on the {3 1 10} surface are also modelled. We assign most electronic peculiarit ies of stepped surfaces to the values of the Madelung potential acting on the under-coordinated atoms, which is a function of their first an d second coordination numbers. An analytical model is proposed to expl ain the bond contractions around these atoms. Finally the microscopic contributions to the step energy are discussed, together with the stre ngth of the step interaction as a function of their separation.