MECHANISM FOR H-2 DISSOCIATION ON TRANSITION-METAL CLUSTERS AND SURFACES

Artikel i vetenskaplig tidskrift, 1989

Basic rules are set up for the requirements on a cluster for dissociatively chemisorbing H2. These rules are built on previous experience from model calculations on transition metal complexes and surfaces. If these rules are combined with the knowledge of the atomic spectra of the transition metals, an understanding of both the low reactivity of the Co6-Co9 clusters compared to the corresponding nickel clusters and the similarly large reactivities of Co10 and Ni10 can be obtained. It is found that all the Co6-Co9 clusters have stable closed valence shell configurations. The present model for dissociating H2 does not involve the electron donation from the cluster to H2 that has been suggested previously. The correlation between ionization energies and reactivities of the clusters is shown to be a secondary consequence of the electronic structure of the clusters.