We have carried out an ab initio study of α-Sn (111), with the aim of predicting and understanding its structure, reconstructions, and electronic states. We consider a variety of structural possibilities, and optimize them by moving atoms according to Hellmann-Feynman forces. Our results indicate that the unreconstructed surface is highly unstable, while a variety of reconstructions compete for the true ground state. Extrapolated trends from diamond to Si to Ge are well borne out, with a 2×1π-bonded chain reconstruction prevailing in the absence of adatoms, and a c(4×2) or (2×2) basic adatom-restatom unit reconstruction otherwise. Accompanying surface bucklings are in both cases larger than in Si and Ge, with consequently large ionic charge transfers predicted. Search for a β-Sn-like metallic state of the surface turned out to be inconclusive. © 1996 The American Physical Society.

• Received 5 December 1995

DOI:https://doi.org/10.1103/PhysRevB.54.11769