Surface states of a semi-infinite diamond crystal limited by the (100) plane

Two kinds of surface states with energies lying in the gap between the valence and the conductive zone, were found for a semi-infinite diamond crystal, limited by the (100) plane, using the MO LCAO method, in which the molecular orbits are expressed as linear combinations ofsp ³ hybrid orbits of carbon atoms. One of these zones of surface states is completely occupied, the other completely unoccupied. The nature of these surface states is discussed and it is shown that the (100) surface of the diamond behaves similarily as if each surface atom had a free electron pair.