Electronic structure of the Si (111) reconstructed surface in the vacancy model

The self-consistent pseudopotential method is applied to the Si (111) 7 × 7 reconstructed surface in the vacancy model with a simplified $\text{3}\text{×}\text{3}$ superlattice structure. Numerical results with and without relaxation of surface atoms are presented. It is concluded that the relaxation, if any, is to be much smaller than the atomic distance to explain the photoemission spectrum of the 7 × 7 surface. The importance of the many-body effect is suggested in the photoemission process associated with the dangling bond surface states of Si.