QUASI-PARTICLE BAND-STRUCTURE OF C(111)2X1 AND C(100)2X1

Quasi-particle band structure calculations are performed for the geometry-optimized diamond (111)2 x 1 and (100)2 x 1 surfaces within the GW approximation. The C(111)2 x 1 surface exhibits a strong reconstruction resulting in rr-bonded chains of surface atoms. However, the precise positions of the chain atoms are still under debate. Ideal, buckled, and dimerized chains are discussed. We find agreement with spectroscopic data, including the correct surface gap, only for the dimerized structure. From an ab initio total energy minimization within DFT-LDA we favour the 2 x 1 symmetric dimer reconstruction for the C(100) surface. The resulting quasi-particle band structure exhibits two well separated (dangling-bond related) surface bands within the fundamental gap.