The surface structure of Si(111)-7 x 7 reconstruction was calculated by using ab initio pseudopotential total-energy technique adopting slab models of different geometries and different thicknesses. It was shown that the converged surface topography could be obtained only when the slab was thick enough: more than five Si layers were allowed to relax. The converged surface topography turns out to be consistent with the experimental results from low-energy electron diffraction, scanning tunnelling microscopy, and noncontact atomic force microscopy. This result reasonably explains the discrepancy between the experimentally observed image contrasts and the previous results from ab initio calculations.

Surface Topography of the Si(111)-7 x 7 Reconstruction. S.H.Ke, T.Uda, K.Terakura: Physical Review B, 2000, 62[15], 15319-22