金钯二元小团簇的几何结构与电子性质

在UBP86/LANL2DZ和UB3LYP/def2-TZVP水平下详细研究了AumPdn(m+n≤6)团簇的几何结构和电子性质.阐明了团簇的结构特征、平均结合能、垂直电离势、垂直电子亲和能、电荷转移以及成键特征.除单取代混合团簇(AunPd和AuPdn,n=5或6)外,五和六原子混合团簇中钯原子趋于聚集到一起形成Pdcore,金原子分布在Pdcore周围形成PdcoreAushell结构.含一个和两个钯原子团簇的电子性质与纯金团簇类似,呈现一定奇偶振荡.混合团簇的电子性质,如最高占据分子轨道(HOMO),最低未占据分子轨道(LUMO),垂直电离势,垂直电子亲和能,Fermi能级和化学硬度等均与团簇空间结构和金、钯原子数之比直接相关.混合团簇中存在钯原子到金原子间的电荷转移,表明团簇中存在明显金钯间成键作用.分析团簇的电荷分布、前线轨道和化学硬度表明,金钯混合团簇对小分子如O2、H2和CO等的反应活性要强于纯金团簇.

Geometric Structures and Electronic Properties of Small Gold-Palladium Binary Clusters

The geometric and electronic properties of Au_mPd_n (m+n ≤6) binary clusters were investigated at the UBP86/LANL2DZ and UB3LYP/def2-TZVP levels of theory. Structural features, binding energies, vertical ionization potentials, vertical electron affinities, charge transfer, and binding characteristics were determined for each Au-Pd binary cluster. For the five- and six-atom Au-Pd binary clusters, except for the mono-substituted mixed clusters (Au_nPd and AuPd_n,n=5 or 6), the palladium atoms combined to form a Pd_(core) and the gold atoms were located around the Pd_(core) to produce the Pd_(core)Au_(shell) structure. The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), vertical ionization potentials (VIP), vertical electron affinities (VEA), Fermi levels, and chemical hardness of the Au_mPd and Au_mPd_2 clusters are similar to those of the pure gold clusters, indicating an odd-even oscillation. The electronic properties of the mixed clusters, such as the HOMO, LUMO, VIP, VEA, Fermi levels, and chemical hardness, are proportional to the spatial structure and the Au/Pd atomic ratio of the mixed clusters. A very large electronic charge transfer from Pd to Au was found for the binary clusters, indicating a bonding interaction between Au and Pd atoms in the mixed cluster. The electronic properties of the Au-Pd binary clusters reveal that the reactivity of the Au-Pd binary clusters toward small molecules, such as O_2, H_2, and CO, is higher than that of the pure gold clusters.