LOW-TEMPERATURE ATOMIC DYNAMICS OF THE SI(111)-7X7

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