STRUCTURE OF CO(H-2)N(+) CLUSTERS, FOR N=1-6

The geometries and H-2 binding energies have been determined for Co(H-2)(n)(+), for n = 1-6. The binding energies are in good agreement with experiment. The shape of the clusters is used to explain the pairwise decrease in the binding energies. The bonding in CoH2+ and Co(H-2)(2)(+) is very similar and is enhanced by sda hybridization. The next two H-2 molecules add to the side of Co(H-2)(2)(+), These two additional H-2 molecules cannot benefit from sd sigma hybridization and are less strongly bound. The addition of the fifth and sixth H-2 molecules eliminates sd sigma hybridization as a mechanism fur reducing Co-H-2 repulsion, This coupled with the smaller Co to H-2 sigma* donation results in another decrease in the binding energies.