“…In addition, this model was found to be unstable in density functional theory calculations [9]. A number of other models have been proposed from first-principles calculations and scanning tunneling microscopy images [3,10,11]. These models generally have a single gold atom substituting for Si * This paper was presented at International Symposium on Surface Science and Nanotechnology (ISSS-5), Waseda University, Japan, 9-13 November, 2008.…”