VIBRATIONAL PROPERTIES OF ALUMINUM, NICKEL AND COPPER SURFACES

The vibrational properties of the (111) surface of aluminum and nickel and all the low-index surfaces of copper are examined. The surface phonon spectrum is calculated using the effective-medium theory to get the total energy and forces of the metallic system. A detailed discussion of the resulting dispersion relations and polarizations is presented together with a comparison to experimental data from electron energy loss and helium scattering experiments. Effective force constants at the surface are calculated and shown to differ from the bulk values in accordance with simple force constant model fits to experiment. We show analytically how these effective force constant changes are a consequence of the many-body character of the inter-atomic interactions in a metallic system.