SURFACE PHONON-DISPERSION OF P(2X2)O NI(111)

Using inelastic electron scattering we have mapped the salient surface phonon features of the p(2 X 2)O/Ni(111) system along the GAMMABAR-MB AR' direction of the surface Brillouin zone. Because of the diffuse sc attering properties of the system, we have developed a maximum entropy deconvolution routine to extract enhanced spectroscopic information f rom the data. With this routine a set of experimental dispersion curve s were successfully obtained for the O/Ni system. We have additionally developed a lattice dynamical model of the system and used spectral d ensity curves from this to produce theoretical dispersion curves for c omparison to the experimentally generated curves. From these compariso ns we conclude that the bonding interactions in the topmost nickel lay ers are well described by a scaling relation which relates intermetall ic force constants and bond length, and that the various bond lengths present in the surface region can be referenced to a single force cons tant description of the bulk Ni-Ni interaction. The surface force fiel d derived in this way for p(2 X 2)O/Ni(111) differs significantly from that of the clean Ni(111) interface.