All-electron relativistic calculations on hydrogen atom adsorption onto small copper clusters

An all-electron scalar relativistic calculation on CunH (n = 1–13) clusters has been performed by using density functional theory with the generalized gradient approximation at the PW91 level. Our results reveal that the hydrogen atom prefers to occupy the two fold coordination site for CunH (n = 2, 4–6, 8, 10–13) clusters, the single fold coordination site for CunH (n = 1, 3, 7) and the three fold coordination site for Cu9H cluster. For all CunH clusters, only the Cu11 structure in Cu11H is distorted obviously. After adsorption, the Cu–Cu bond is strengthened and the Cu–H bond of odd-numbered CunH clusters is relatively stronger than that of adjacent even-numbered CunH clusters. The Cu–Cu bond-length and Cu–H bond-length for all CunH clusters of our work are significantly shorter than those of previous work. This discrepancy can be explained in terms of the scalar relativistic effect. The most favorable adsorption between small copper clusters and hydrogen atom takes place in the case that hydrogen atom is adsorbed onto an odd-numbered pure Cun cluster and becomes CunH cluster with even number of valence electrons. The odd–even alteration of magnetic moments is observed in CunH clusters and may provide the material with tunable code capacity of “0” and “1” by adsorbing a hydrogen atom onto odd- or even-numbered copper clusters.