5d过渡金属原子中心镶嵌Ag团簇M@Ag12(M＝Hf～Hg) Ih和Oh构型的密度泛函理论研究

采用相对论密度泛函理论方法对Ih和Oh构型M@Ag12 (M＝Hf～Hg)的几何和电子结构进行了系统的研究. 研究表明, 原子半径之和与团簇的电子结构共同决定了M—Ag键长的大小. M@Ag12的成键能来自中心原子的嵌入能和Ag12笼子的形变能. 最高占据轨道为成键轨道的团簇比反键轨道的团簇的稳定性强. 我们发现在此系列中, Ih构型不一定总比Oh构型稳定. Hf@Ag12, Ir@Ag12, Au@Ag12和Hg@Ag12的Oh构型比Ih构型稳定.

A DFT Study of 5d Transition Metal Impurities Encapsulated in the Icosahedral and Cuboctahedral Ag12 Cages

The geometrical and electronic structures of 5d transition metal (TM) impurities encapsulated in the icosahedral and cuboctahedral Ag12 cages have been investigated systematically by a relativistic density functional theory method. Calculated results show that the M—Ag bond lengths depend on two factors: the sum of atomic radii and the cluster’s electronic structure. The binding energy of M@Ag12 varies with the embedding energy of M into Ag12 cage and with the distortion energy of the originally empty Ag12 cage upon embedding the M atom. The clusters with bonding HOMO are more stable than those with anti-bonding HOMO. It was found that the icosahedral clusters were not always more stable than their cuboctahedral isomers, while the cuboctahedral clusters of Hf@Ag12, Ir@Ag12, Au@Ag12 and Hg@Ag12 were more stable than their icosahedral isomers.