Binding sites for the adsorption of a single Si atom upon the reconstructed (100) surface were identified by performing first-principles total-energy calculations. Several saddle-points were identified, for the migration of the adatom, by mapping the total energy as a function of its position on the surface. An activation energy of 0.6eV was found for diffusion parallel to dimer rows on the surface. For diffusion perpendicular to the rows, the activation energy was 1eV.

G.Brocks, P.J.Kelly, R.Car: Physical Review Letters, 1991, 66[13], 1729-32