Abstract
The electronic surface structure has been studied of a binary compound in the zincblende structure with GaAs as a prototype. Two models are presented: (i) a one-orbital s-like model and (ii) a three-parameter four-orbital sp3 model. Various kinds of surface states are found and analysed: dangling bonds, back bonds and intrinsic atomic-like states. Both surfaces, the (111)-ga and the (1?1?1?)-as, are discussed and their similarities and differences emphasized. Comparison with experiment yields good qualitative agreement.