Surface states and the local electronic structure at surfaces

Applications of various theoretical approaches to surface electronic structure are reviewed, with particular emphasis on atomic-orbital-based methods. On some surfaces the different atomic environment in comparison with the bulk leads to electronic wavefunctions that are localized in the surface layers; on other surfaces the local density of states (LDOS) exhibits significant surface-induced features, although there are no true surface-localized states. In either case the surface electronic structure can have important consequences for surface relaxation, reconstruction (including surface-defect properties) and reactivity. Examples are chosen from covalent elemental and compound semiconductors; simple, transition and noble metals and their alloys; transition metal oxides, nitrides and carbides; and chemisorbed species on surfaces.