Ab initio calculation of the structure, electronic states, and the phonon dispersion of the Si(100) surface

We have investigated the structural, electronic, and dynamical properties of the Si(100) surface within the density-functional theory. Our calculations are based on the plane-wave pseudopotential method combined with the slab supercell description for the surface. With the help of the Hellmann-Feynman forces, we have determined the equilibrium positions and the total energies of the tilted dimer p(2 x 1), p(2 x 2), and c(4 x 2) geometries. The higher-order reconstructions are similar in energy and slightly favored above the asymmetric p(2 x 1) configuration. The calculated electronic structure of the p(2 x 2) and c(4 x 2) surfaces compares very well with the experimental data from photoemission spectroscopy, An ab initio linear-response formalism has been used to determine the phonon dispersion curves of the tilted dimer Si(100) p(2 x 1) surface along the high-symmetry directions of the surface Brillouin zone. A comparison of our results with the additionally calculated phonons at the (J) over bar point of the c(4 x 2) arrangement shows only small differences which arise from correlation along the dimer rows. We also observe a low-frequency dimer twisting mode which is expected to support dimer flipping processes.