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

Quasi-particle band structure calculations are performed for the geome try-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 reconstructi on resulting in rr-bonded chains of surface atoms. However, the precis e positions of the chain atoms are still under debate. Ideal, buckled, and dimerized chains are discussed. We find agreement with spectrosco pic data, including the correct surface gap, only for the dimerized st ructure. From an ab initio total energy minimization within DFT-LDA we favour the 2 x 1 symmetric dimer reconstruction for the C(100) surfac e. The resulting quasi-particle band structure exhibits two well separ ated (dangling-bond related) surface bands within the fundamental gap.