THE VIBRATIONAL DYNAMICS OF THE ORDERED METALLIC Pd/Cu(100) SURFACE ALLOYS

The vibrational properties of the three ordered metallic surface alloys, Cu(100)-c(2 × 2)-Pd, Cu(100)-(2 × 1)-Pd, and Cu(100)-(2 × 2)-Pd, are presented. The phonon dispersions of vibrational modes as well as the local density of phonon states (LDOS) are calculated using matching theory associated with Green's function formalism. The calculated results are discussed and interpreted. In particular, the transfer of charge between the Pd and Cu atoms in the surface alloys modifies the surface boundary force constants, with resultant remarkable differences for the vibrational LDOS on the Pd and Cu atomic sites at the Pd/Cu(100) surface, compared to the LDOS at the pure Cu(100) surface. This may favor new Pd-catalyzed reactions at such surface alloys systems.