ELECTRONIC-STRUCTURE OF CLEAN INSULATING OXIDE SURFACES .1. A NUMERICAL APPROACH

Systematic trends in the surface electronic structure of simple insula ting oxides are studied thanks to a quantum self-consistent numerical approach. Four oxides of various ionicity have been chosen: SrO, MgO, rutile TiO2 and alpha-quartz SiO2, and for each of them, several surfa ces, involving atoms with different coordination numbers, have been mo deled: the (100), (110) and (211) faces of the rocksalt oxides, the (1 10), (100) and (001) faces of rutile and the (0001) and (10 $($) over bar$$ 10) faces of quartz. We discuss the competition between electros tatic and covalent processes, through an analysis of the density of st ates characteristics, the gap width, the ionic charges and the surface energy.