First-principles calculations of theSi(111)−c(2×8)surface

Abstract

We present results of a first-principles total-energy calculation of the $\mathrm{Si}(111)\ensuremath{-}c(2\ifmmode\times\else\texttimes\fi{}8)$ reconstruction. This structure has been observed in the quenched Si(111) surface. Similar to the case of $\mathrm{Ge}(111)\ensuremath{-}c(2\ifmmode\times\else\texttimes\fi{}8)$, the surface unit cell presents asymmetries, related to small inequivalences of the rest atoms, adatoms, and first bilayer atoms. These asymmetries are mainly in the surface plane, but a small buckling of the rest atoms is also found. The inequivalences in the unit cell produce a splitting of the rest-atom dangling bond state, which explains the apparent difference in the atomic size of the rest atoms as seen in recent STM experiments.