Calculations were performed for the Si(111)-7×7 surface reconstruction model proposed by Takayanagi et al. The structure contains dimers, adatoms, and stacking faults (DAS) in the surface layer. The DAS model has 19 dangling bonds and 12 ‘‘top site’’ adatoms per 7×7 unit cell. In the tight-binding based energy-minimization calculation, Hellmann-Feynman forces were used to relax adatoms and three layers of a five-layer 7×7 slab configuration. The surface energy is found to be at least 0.40 eV per 1×1 cell lower than that of an ideal and unrelaxed Si(111) surface, as compared to 0.36 eV for the π-bonded chain structure for the 2×1 cleaved surface. This is the lowest surface energy calculated for the Si(111) surface. Atomic configurations were obtained for the completely relaxed system. The calculated surface electronic density of states and the atomic origin of the surface electronic structure are in good agreement with experimental data.