Theoretical study of chemisorption of carbon monoxide on copper clusters

The behavior of the chemisorption energy with cluster size has for the first time been investigated for geometry-optimized clusters. It is found that for the case of carbon monoxide adsorbed on Cu clusters, both neutral and cationic, the cluster size oscillations of the chemisorption energies were strongly reduced by geometry optimization of the clusters. An interesting aspect of the results is that clear shell closing effects are observed for Cu sub 6 CO and Cu sub 7 exp + CO, where the C lone-pair electrons participate in the electronic shells. These results constitute further evidence for the recent finding that the electrons of the adsorbate should fit into the electronic structure of the cluster to correctly model infinite surface results. The variation of the chemisorption energy with the coordination number of the metal atom at the adsorption site is discussed in relation to recent experiments.