All-electron scalar relativistic calculation of water molecule adsorption onto small gold clusters

An all-electron scalar relativistic calculation was performed on Au (n) H2O (n = 1-13) clusters using density functional theory (DFT) with the generalized gradient approximation at PW91 level. The calculation results reveal that, after adsorption, the small gold cluster would like to bond with oxygen and the H2O molecule prefers to occupy the single fold coordination site. Reflecting the strong scalar relativistic effect, Au (n) geometries are distorted slightly but still maintain a planar structure. The Au-Au bond is strengthened and the H-O bond is weakened, as manifested by the shortening of the Au-Au bond-length and the lengthening of the H-O bond-length. The H-O-H bond angle becomes slightly larger. The enhancement of reactivity of the H2O molecule is obvious. The Au-O bond-lengths, adsorption energies, VIPs, HLGs, HOMO (LUMO) energy levels, charge transfers and the highest vibrational frequencies of the Au-O mode for Au (n) H2O clusters exhibit an obvious odd-even oscillation. The most favorable adsorption between small gold clusters and the H2O molecule takes place when the H2O molecule is adsorbed onto an even-numbered Au (n) cluster and becomes an Au (n) H2O cluster with an even number of valence electrons. The odd-even alteration of magnetic moments is observed in Au (n) H2O clusters and may serve as material with a tunable code capacity of "0" and "1" by adsorbing a H2O molecule onto an odd or even-numbered small gold cluster.