Electronic structure of the (111) surface of diamond: Solution by self-consistent many body calculation

We present a first-principles calculation of the geometry and of the electronic structure for the C(111)2x1 ⫻ 1兲 surface. We find that this surface reconstructs with ␲ -bonded chains without any significant dimerization or buckling. At the DFT level, it appears semimetallic, in agreement with previous calculations, but in contrast to experimental evidence. Even the introduction of quasi-particle corrections within the usual GW scheme does not lead to the opening of the gap between surface states. Quasiparticle corrections to the surface band structure are hence calculated within a self-consistent GW scheme. A gap of about 1 eV is found between the surface states, thus finally solving the discrepancy between theory and experiment.