Intrinsic surface electronic energy states for the ideal (1 x 1), relaxed (1 x 1) and reconstructed (2 x 1) (111) surfaces were successfully calculated by using a self-consistent scattered-wave cluster model. For both ideal and relaxed structures, three bands of surface states were found. For (2 x 1) reconstruction, the dangling-bond surface band splits into 2 overlapping bands. The results accounted for all of the observed features observed in photo-emission experiments on Si(111) surfaces.

Effect of Relaxation and Reconstruction on the Electronic-Energy-Level Structure of the Si(111) Surface. I.P.Batra, S.Ciraci: Physical Review Letters, 1975, 34, 1337-40