SURFACE VIBRATIONAL PROPERTIES IN THE PRESENCE OF DEFECTS AND ADSORBATES

A perfect surface covered by defects such as adsorbed atoms or vacancies is studied. We take account of the statistical distribution of the defects lying on sites. We show that the surface phonon lines are shifted and broadened and that resonances in the projected bulk phonon region are affected in their positions and widths. These effects depend upon the strength of the forces between adatom and crystal atoms and on the correlation function of adatom positions. They can be observed experimentally even with a small adatom coverage. © 1990 Pergamon Press plc.