Structure and energetics of Ge(111) c(2 × 8) reconstruction

Abstract

We present self-consistent MNDO calculations of atomic clusters modelling the structure of adatom generated 2 × 2, √3 × √3 and 2 × 8 reconstructions of the Ge(111) surface. Comparisons are made of the T4 and H3 adsorption sites and of closed shell singlet and open shell (spin triplet) RHF wavefunctions. We find that √3 × √3 prefers the T4 site energetically, but 2 × 2 prefers H3. Subsurface relaxation up to three layers deep plays a crucial role in the energetics and we also find significant charge transfers between rest atoms and adatoms as well as between layers. A consistent interpretation can be given of the similarities and differences between the configurations in terms of bond rehybridization and polarization effects as well as the different surface topologies.