Ab initio calculations of the $2\times 1$, $c(2\times 8)$, and $7\times 7$ reconstructions of the diamond, Si, and Ge(111) surfaces are reported. The $\pi$-bonded chain, adatom, and dimer-adatom-stacking fault models are studied to understand the driving forces for a certain reconstruction. The resulting energetics, geometries, and band structures are compared for the elemental semiconductors with different atomic sizes, and chemical trends are derived. We show why the lowest-energy reconstructions are different for the group-IV materials considered.

• Received 9 February 2001

DOI:https://doi.org/10.1103/PhysRevLett.87.016103