Theoretical study of the Si(100) surface reconstruction

We present the results of a systematic study of the reconstruction of the Si(100) surface based upon total energies calculated within the framework of the local-density approximation. We focus on the extent to which total energy differences may be calculated reliably by examining these differences for the ideal surface and four proposed reconstructions: p(2×1) symmetric, p(2×1) asymmetric, p(2×2), and c(4×2). The calculations were performed using norm-conserving pseudopotentials and a plane-wave basis. The convergence of the total energy differences was assessed by varying the energy cutoff used to truncate the plane-wave basis and the number of sampling points used to perform Brillouin zone (BZ) integrals over a large range. The effect of optimizing atomic geometries as a function of the energy cutoff and density of BZ sampling points was determined. With the exception of the p(2×2) and c(4×2) reconstructions, whose energies only differ by 3 meV per dimer, we are able to unambiguously determine the energy ordering of the five systems studied. Disagreements between previous calculations can be largely understood in terms of the different energy cutoffs and BZ samplings used. The electronic structures of the different reconstructions are calculated and compared.