ELECTRONIC-STRUCTURE OF SI(100)C(4X2) CALCULATED WITHIN THE GW APPROXIMATION

The electronic structure of the Si(100)c(4 X 2) surface has been calcu lated using a quasiparticle formalism in which the self-energy is eval uated in the GW approximation. The calculated surface state dispersion s and band gaps are in good agreement with experiments. The results su pport the existence of correlated dimer buckling at room temperature. The equilibrium c(4 X 2) sur-face obtained from total-energy calculati ons is 0. 14 eV/dimer lower in energy than the 2 X 1 symmetric dimer s urface, exhibits a dimer buckling of 0.69 angstrom, and has a surface energy of 1.39 eV/(l X 1).