水分子在Yn (n=2-8)团簇表面的分子吸附与解离吸附

运用密度泛函理论，对H2O在Yn (n=2-8) 团簇表面的分子吸附与解离吸附两种模式进行了结构优化，电子性质分析。结果表明：分子吸附中H2O倾向于O端吸附于Y-Y原子桥位，而解离吸附中H2O解离的H, O原子倾向于吸附于Yn团簇的面位。两种吸附模式都导致了（解离吸附n=4, 5除外）主团簇Y原子平均键长增大。分子吸附和解离吸附的吸附强度和化学活性都随尺寸增加而增大。解离吸附中体系的稳定性明显高于分子吸附，且与体系的电子壳层效应密切相关。

Difference between molecular adsorption and dissociated adsorption of H2O on the Yn (n=2-8) clusters

The difference between molecular adsorption and dissociated adsorption of water molecule on the surface of yttrium clusters has been investigated with the generalized gradient approximation based on the density functional theory. The results show that the O atom of H2O is seen to be adsorbed on the Y-Y bridge sites for molecular adsorption, while the isolated O and H atoms tend to locate at the face sites of Yn clusters for dissociated adsorption. The average bond length between Y-Y atoms of Yn clusters is elongated in most cases for both adsorption models. Both the adsorption strength and chemical activity for the two adsorption models are improved as the increase of cluster size. The stability of dissociated adsorption is obviously higher than that of molecular adsorption in all of the sizes, and is closely associated with the effects of electronic shell.