Local density approximation calculations were used to determine the electronic properties and surface band structure of the Si(111)-(7 x 7) surface. A 2-dimensional model was introduced in order to describe the correlation properties of the electrons which were localized in the surface adatom dangling bonds. Analysis of this model showed that the Si(111)-(7 x 7) surface had a metallic character and exhibited large correlation effects that arose from the localization of electrons on elementary structures with an hexagonal ring geometry.

Electron correlation effects in the Si(111)-7 x 7 surface J.Ortega, F.Flores, A.L.Yeyati: Physical Review B, 1998, 58[8], 4584-8