Hydrogenation of aluminium hexamer: Ab initio molecular orbital theory and density functional theory study

The detailed mechanism of the reaction of aluminium hexamer with H2 molecule to form a dihydride has been studied using ab initio molecular orbital theory and density functional theory. For the bare Al6 cluster, the singlet state distorted octahedron (D3d) is found to be the ground-state structure. The hydrogenation reaction of the singlet state Al6 cluster is described by the lack of activation barrier for H2 cleavage, consistent with experiment. The most stable product isomer involves two H bridges on the Al–Al edges of the same Al–Al–Al face of the Al6 octahedron and its formation is exothermic by about 30 kcal/mol.