Electronic structure of buckled and vacancy models of Si(111)-7 × 7 surface by DV-Xα cluster method

Electronic structures are calculated for two typical reconstruction models of the Si(111)-7 × 7 surface, i.e. the buckled and the vacancy models. The first-principles discrete variational DV-X alpha calculations are carried out for the surface cluster without a vacancy (Si13H15) and with a vacancy (Si12H15). Essential characteristics in the electronic structure are elucidated which are closely related to surface atomic arrangements. The low-density vacancy model recently proposed by Ino (1980) is pointed out to be a promising reconstruction mode for the Si(111)-7 × 7 surface.