AB-INITIO CALCULATION OF THE ATOMIC AND ELECTRONIC-STRUCTURE FOR THE CLEAN 3C SIC (110) 1X1 SURFACE

We report results obtained by a systematic study of the geometry and the electronic structure of bulk SiC polytypes and the clean, but relaxed 3C SiC(110) 1 x 1 surface, using the parameter-free density-functional theory (DFT) within the local-density approximation (LDA) and norm-conserving, fully separable, ab initio pseudopotentials. Soft pseudopotentials for carbon atoms are derived to reduce the cut-off of the underlying plane-wave expansion and tested with respect to ground-state properties of 3C SiC. Despite the gap problem occurring within DFT-LDA, we discuss the bulk bandstructures resulting for polytypes with small unit cells. The 3C SiC(110) 1 x 1 surface is simulated by a slab geometry wherein the atomic positions of the uppermost layers are optimized by minimizing the total energy, using a Car-Parrinello-like approach. The resulting equilibrium geometries (bond lengths and angles) and the accompanying electronic structure are discussed within the context of available data. Further, the changes of the electronic structure with respect to that obtained for bulk SiC and the effect of surface relaxation are considered in detail.