First-principles calculations of beta-SiC(001) surfaces

We report self-consistent nb initio Calculations of structural and electronic properties for five different configurations of polar beta-SiC(001) surfaces. Both Si- and C-terminated structures are investigated. We employ our smooth norm-conserving pseudopotentials in separable form within the local-density approximation of density-functional theory. Gaussian orbital basis sets are used in the supercell calculations. For the Si-terminated (2x1) surface we do not find any significant dimerization of the surface-layer Si atoms. For various C-terminated surfaces, on the contrary, we find strong carbon dimers as the basic building blocks of the reconstruction. Our optimized configurations for C-terminated surfaces are in good general agreement with structural models from the literature that have been suggested on the basis of experimental data. Our results for the Si-terminated (2x1) surface, on the contrary, show significant differences from suggested models. We discuss the physical origins of the distinctly different reconstruction behavior of Si- and C-terminated surfaces and present a full account of surface electronic properties of these systems including the quasiparticle band structure of the C-terminated beta-SiC(001)-(2x1) surface as resulting in the GW approximation. We present and discuss our results in comparison with other theoretical results and with experimental data from the literature.