Abstract
Phonon dispersion data on Ni(100) for the (011) direction are calculated using the matching procedure. The Rayleigh mode is shown to be a surface state over the whole of the two-dimensional Brillouin zone, and a new odd surface state is found. The Van Hove singularities are analysed in detail and a practical definition of surface resonances is given. A new initial condition describing the scattering of an incoming bulk phonon by the surface is introduced. The calculated dispersion curves of surface resonances are compared with other authors' work. Eventually a new interpretation of EELS data is proposed.