PHONON-SPECTRA AND MEAN-SQUARE DISPLACEMENTS ON CU(11N) VICINAL SURFACES

Surface phonon spectra on Cu(11n) vicinal surfaces, with odd number n = 1 to 19, are studied by using the continued fraction method and embe dded atom potentials. Vibration frequencies for atoms at step edges ar e found to be softer along the surface normal and the step normal dire ctions than those of terrace atoms and bulk atoms. Stiff frequencies a long the surface normal direction are found for those atoms (with bulk nearest neighbors) located just beneath the step atoms. We find that surface relaxation induces 20-35% stiffening in the force constants of stepped surface atoms. The mean-square displacements (MSD) for atoms at vicinal surfaces are calculated at different temperatures. The surf ace MSD is found to be isotropic for the (100) surface and anisotropic for the (11n) surfaces.