A first-principles molecular dynamics study was made of the surface structure and atomic dynamics of Ge(111)c(2 x 8) at 0 and 300K. The T = 0 ground-state structure exhibited asymmetries between the two adatoms and the two rest atoms in the surface unit cell, which were seen experimentally using low-energy electron diffraction. These asymmetries, which were found to survive at ∼300K, led to zone folding and splitting of the surface phonon modes. Two pairs of prominent surface modes were identified; localized mostly on the adatoms and second-layer atoms just below. The values of the mean-square displacements for the various layers at various temperatures indicated enhanced surface anharmonicity with respect to the bulk.

Atomic Dynamics and Structure of the Ge(111)c(2 x 8) Surface. N.Takeuchi, A.Selloni, E.Tosatti: Physical Review B, 1995, 51, 10844-50