Model calculation of the electronic structure of a (111) surface in a diamond-structure solid

The authors present exact results for a model calculation of the surface electronic structure of a (111) face of a diamond-type solid. The model contains only one s-state per atom, but allows for surface rearrangement both at the outer layer and at the outer bounds. Two kinds of surface states are found. The first kind are localized at the outer bounds and split off the bulk bands as the bond potential increases beyond a critical value. The second kind are intrinsic surface states and exist independently of the surface rearrangement but only in a restricted domain in the Brillouin zone where structure factors are smaller than 1. These intrinsic states have not been discussed before; they exist also in more realistic hybrid models of diamond-structure solids.