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 t he electronic structure of bulk SiC polytypes and the clean, but relax ed 3C SiC(110) 1 x 1 surface, using the parameter-free density-functio nal theory (DFT) within the local-density approximation (LDA) and norm -conserving, fully separable, ab initio pseudopotentials. Soft pseudop otentials for carbon atoms are derived to reduce the cut-off of the un derlying 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 smal l unit cells. The 3C SiC(110) 1 x 1 surface is simulated by a slab geo metry wherein the atomic positions of the uppermost layers are optimiz ed by minimizing the total energy, using a Car-Parrinello-like approac h. 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 w ith respect to that obtained for bulk SiC and the effect of surface re laxation are considered in detail.