The structural transformations of dimer rows on 2 x 1 reconstructed (001) surfaces were investigated by means of  ab initio  quantum theoretical calculations. It was revealed that the adsorption of Li or H atoms produced buckling of the dimer at the adsorbed site. This buckling then propagated along the dimer row so as to produce a zig-zag dimer-row structure. Extra filled-state and empty-state band structures appeared near to the Fermi level, which consisted of occupied and unoccupied molecular orbitals that were localized on the upper-side and lower-side Si atoms of buckled dimers, respectively. Scanning tunnelling microscopic images of zig-zag dimer rows on (001) surfaces were shown to reflect the spatial distributions of electrons in these extra bands. The propagation of buckling was explained in terms of the electron distribution on the surface, and dimer-row structures at low or room temperature were also considered.

T.Hoshino, M.Hata, S.Oikawa, M.Tsuda, I.Ohdomari: Physical Review B, 1996, 54[16], 11331-9