Interaction and vibrations of CN^- chemisorbed on CU(100):theoretical studies

Cluster models have been used to study the interaction of CN- with Cu(100) at an on top site. The CN- inter-nuclear axis has been taken normal to the surface and orientations with both C nearest and N nearest the surface have been considered using a Cu5 substrate cluster. The electronic wave functions of the clusters were obtained with ab initio Hartree-Fock-LCAO methods. The Cu-CN- binding energy is found to be very similar for both CN- orientations. An analysis of the CN- -metal interaction shows that electrostatic and polarization contributions due to the charge of CN- are most important for the binding while σ charge transfer from CN- to the metal is the largest donation contribution. The effects of the CN--metal interaction on the vibrational frequencies of CN- are similar for the two orientations but the effective charges of the vibrations are rather different. This can be explained on the basis of a detailed charge analysis in the clusters. © 1986.