Vibrational spectrum of vicinal surfaces.

Abstract

The vibrational spectrum of FCC metal vicinal surfaces is obtained from displacement-displacement Green's functions. Results are presented for the Pt(332) surface. Surface spectral densities are calculated, in the neighbourhood of the surface, for selected directions in the Brillouin zone. The coherent surface vibrations contain features that reproduce the available experimental results and predict others that might be observable by He scattering. The dispersion relation of a high frequency surface mode is calculated. The surface mode frequency is shown to depend weakly on the wave-vector along high symmetry lines in the surface Brillouin zone. The polarization and local character of this mode are closely related. Near the Brillouin zone centre and also near the zone boundary it is strongly polarized perpendicularly to the surface and a sudden polarization change is seen when its frequency approaches the surface projection of the bulk spectrum.