We present results of a first-principles molecular-dynamics study of the surface structure and atomic dynamics of Ge(111)c(2×8) at T=0 and T=300 K. The T=0 ground-state structure shows asymmetries between the two adatoms and the two restatoms in the surface unit cell, which are seen experimentally in low-energy electron diffraction. These asymmetries, which are found to survive at T∼300 K, lead to zone folding and splitting of the surface phonon modes. Two pairs of prominent surface modes are identified, mostly localized on the adatoms and second-layer atoms just below. The values of the mean square displacements for the various layers at different temperatures moreover indicate an enhanced surface anharmonicity with respect to the bulk.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics