An  ab initio  multi-center molecular dynamics method was used to calculate the surface energies of dimer vacancy lines that were formed on the (100)-(2 x 1) surface by sputtering or etching. The results showed that the optimum widths of dimer vacancy lines perpendicular to the dimer rows were equal to 2 and 3 missing dimers. The results also showed that, at higher vacancy concentrations, dimer vacancy lines parallel to the dimer rows (so-called vacancy islands) - with widths that were greater than 3 missing dimers - were favoured over perpendicular dimer vacancy lines. These predictions were in agreement with experimental observations.

M.H.Tsai, Y.S.Tsai, C.S.Chang, Y.Wei, I.S.T.Tsong: Physical Review B, 1997, 56[12], 7435-8