Physisorption and dissociative chemisorption of H

We have studied the interaction of Al$_{13}^{-}$ anion cluster with H2. Both the long range interaction and dissociative adsorption have been examined using the established correlated ab initio methods, MP2 and CCSD(T), in conjunction with the augmented correlation consistent basis sets up to aug-cc-pVTZ. The formation of the weakly bound (physisorbed) end-on anion complex Al$_{13}^{-}$...H2 is predicted for the interacting Al...H distances of 3.95 Å with the H-H axis pointing towards the `hollow' site of Al$_{13}^{-}$ and binding energy ($D_{e})$ of 0.7 kcal/mol at the estimated complete basis set (CBS) limit of CCSD(T). The barrier height for H2 dissociation on Al$_{13}^{-}$ of 41.6 (42.9) kcal/mol calculated at the ZPVE-corrected CCSD(T)/aug-cc-pVTZ (estimated CCSD(T)/CBS) level is at least twice as large as that evaluated by us for a dissociative adsorption of H2 on an open-shell Al13 neutral cluster. To our knowledge, this report presents the first “benchmark” quality study of the physisorption and dissociative chemisorption of molecular hydrogen on Al$_{13}^{-}$ anion cluster