A theoretical case study: the Sn/Ge(111)-(3 × 3) surface

We present a theoretical analysis of the Sn/Ge(111)-(3 × 3) surface. The (3 × 3) atomic structure is searched using a combination of local-orbital and plane-wave density functional methods. We find a ground state geometry that presents two different types of Sn adatoms whose vertical positions differ by ~0.3 Å. The electronic structure of the surface is analysed including electron correlation effects. The comparison with recent experimental studies, both on the atomic and electronic structure of this surface, gives a strong support to the structural model presented in this work.