Molecular dynamics of Rayleigh waves in Lennard-Jones crystals

The frequency- and wave-vector-dependent spectral densities of the displacement correlation functions for atoms at the surface and at the midplane of a slab consisting of twenty-one (001) layers of an fcc crystal are calculated at two temperatures by means of a molecular-dynamics computer simulation. The atoms in the slab interact through Lennard-Jones (6-12) potentials, and anharmonic effects of all orders are taken into account. The dispersion and lifetimes of the Rayleigh waves on the surfaces of the slab are determined, as well as the changes in the interplanar spacings in the vicinity of the surfaces