A density functional theory study on the H 2S molecule adsorption onto small gold clusters

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An all-electron scalar relativistic calculation on Au n H 2S ( n = 1–13) clusters has been performed by using density functional theory with the generalized gradient approximation at PW91 level. The small gold cluster would like to bond with sulfur in the same plane and the H 2S molecule prefers to occupy the on-top and single fold coordination site in the cluster. The Au n structures and H 2S molecule in all Au n H 2S clusters are only slightly perturbed and still maintain their structural integrity. After adsorption, the S–H, H–H bond-lengths and most Au–Au bond-lengths are elongated, only a few Au–Au bond-lengths far from H 2S molecule are shortened. The reactivity enhancement of H 2S molecule is obvious and the strong gold–sulfur bond is observed expectedly. The most favorable adsorption takes place in the case that the H 2S molecule is adsorbed by an even-numbered Au n cluster and becomes Au n H 2S cluster with even number of valence electrons. It is believed that the strong scalar relativistic effect is favorable to H 2S molecule adsorption onto small gold clusters and is also one of the important reasons for the strong gold–sulfur bond.