Hydrogen adsorption and dissociation on small Al

We present density functional calculations of H2 adsorption and dissociation on small-sized AlnAu clusters for n = 1−13. The growth pattern for AlnAu (n = 2−5,7,12,13) clusters is Au atom occupying a peripheral position of Aln clusters. And the growth pattern for AlnAu (n = 6 and 10) clusters is Au-substituted Aln+1 clusters. It is found that the Au atom substituted the surface atom of Aln+1 cluster and occupies a peripheral position. H2 is easily physically absorbed on the top Au atom of AlnAu clusters with an end-on orientation rather than side-on orientation because of the more effective orbital overlap in the end-on orientation. The reaction of AlnAu with H2 would produce AlnAuH2 because of large exothermic energy changes and relatively small activation energies especially for Al3Au and Al7Au, which might serve as highly efficient and low-cost catalysts for hydrogen dissociation