Low-temperature atomic dynamics of the Si(111)-7x7

We present a large-scale fully ab initio molecular-dynamics study of dynamical properties of the Takayanagi reconstructed Si(111)-7 x 7 surface. The simulation reproduces well the experimentally determined features of the phonon spectra, clarifies their nature and origin, and predicts several additional modes. Correlations are found between these dynamical properties and elements of the local electronic structure of the adatom dangling bonds. Pie find evidence of important anharmonic effects below room temperature. Use of nontraditional signal-processing methods allows for a considerable insight into the details of the dynamics from a short-duration molecular-dynamics trajectory. Results of this analysis significantly extend and modify the results of the previous studies based on more simplified models.