Clustering of hydrogen molecules around a molecular cation:: The Li3+(H2)n clusters (n=1-6)

Ab initio calculations for the lowest-energy isomers of the clusters Li-3(+)(H-2)(n) (n = 0-6) show that the first shell of H-2 molecules is formed by attaching from one to four molecules independently to each vertex of the triangular Li-3(+) core. For 2 less than or equal to n less than or equal to 6, several isomers are possible, depending on how the n ligands are distributed among the three vertexes. The binding energies are very similar to those obtained for the Li+(H-2)(n) clusters, and they vary from 3 to 1.5 kcal/mol, depending on the size of the cluster. The reaction of formation of the cluster is more exothermic at temperatures between 150 and 200 K.