Dynamic factors in the reactions between the magic cluster Al −13 and HCl/HI

Abstract

The icosahedral Al⁻₁₃ is a “magic” cluster with remarkable stability due to its high symmetry and closed valence shells. Its reactivity has provided a molecular model for understanding oxidation and dissolution processes in bulk metals. By first principles calculations, we demonstrated the importance of dynamic factors in the Al⁻₁₃ + HX reactions, with HX being either HCl or HI. There was a barrier to the dissociative adsorption of HX on the surface of an Al⁻₁₃cluster, which involved charge transfer from Al⁻₁₃. Furthermore, the H atom could be bonded to the cluster in multiple ways, similar to the top, bridge and hollow adsorption sites on Al(111) surface. With a large amount of energy (∼40 kcal mol⁻¹) deposited during the formation of Al₁₃HX⁻, the H atom could easily migrate among these sites, similar to the diffusion of hydrogen on metal surfaces. These factors were therefore important considerations in the formation and dissociation of Al₁₃HX⁻, and more generally in reactions involving other metal clusters.