Do we know the true structure of Ge(111)c(2×8)?

We present the first ab initio determination of the surface structure and electronic properties of Ge(111)c(2×8). New features emerge, in addition to the basic adatom rest-atom architecture. In agreement with LEED, which shows weak but nonvanishing quarter-order reflections, we find that an asymmetry is present in the surface unit cell, related to a small buckling between the two rest atoms, as well as to in-plane asymmetries of the rest atoms, adatoms, and first bilayer atoms. This inequivalance also produces a splitting of both the rest-atom and the adatom dangling-bond states, which explains the difference in their apparent heights as seen recently with scanning tunneling microscopy.