An ab initio determination was made of the surface structure and electronic properties of Ge(111)-c(2 x 8). New features emerged in addition to the basic adatom–rest-atom architecture. In agreement with low-energy electron diffraction, which exhibited weak but non-vanishing quarter-order reflections, it was found that an asymmetry was present in the surface unit cell. This was 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 produced a splitting of both the rest-atom and the adatom dangling-bond states; which explained the difference in their apparent heights, as seen using scanning tunnelling microscopy.

Do We Know the True Structure of Ge(111)c(2 x 8)? N.Takeuchi, A.Selloni, E.Tosatti: Physical Review Letters, 1992, 69, 648-51