Abinitio Molecular Dynamic Relaxation Applied To The Silicon(111)-5x5 Surface Reconstruction

We have applied first-principles molecular dynamical relaxation to the Si(111) surface in the 5 x 5 dimer-adatom-stacking-fault structure. We have determined the relaxed atomic surface geometry and the corresponding electronic structure. We find that the filled adatom dangling-bond states are segregated, with the charge density residing on the faulted side of the unit cell, and that the adatoms on the faulted side are higher than the adatoms on the unfaulted side. Surprisingly, we find that, at low temperature, the adatoms on each side of the unit cell are corrugated in a variety of patterns.