Surface phonon calculation of the (111) Ni surface with adsorbed Oxygen

In the framework of a central and angular force constant model we have evaluated the phonon spectrum and the loss function of the Ni (111) surface with p(2×2) and ( )R30° adsorbed lattices of Oxigen. The calculations compare well with recent EELS experimental data. We give reason of the different origin of the weaks observed in the measured spectra in terms of either the modes of the substrate or of the modes induced by the adsorbate.