First-principles finite-temperature simulation of surface dynamics: Si(111)-(7x7)

Methods to extract information on atom dynamics from a short-duration molecular dynamics simulation based on non-traditional signal-processing methods are discussed and illustrated on the dynamics of the (7 x 7) reconstructed Si(111) surface. The results of the ab initio simulation allow an unambiguous assignment of the experimental vibration spectra and predict several new modes. Correlations are found between dynamical properties and the local electronic structure of the adatom dangling bonds. In addition, evidence is found for pronounced anharmonic effects well below room temperature, which can be traced back to soft adatom bonds.