金钯二元小团簇的几何结构与电子性质

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

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.

The geometric and electronic properties of AumPdn （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-Pdbinary clusters, except for the mono-substituted mixed clusters （Au,,Pd and AuPd,, n=5 or 6）, the palladium atoms combined to form a Pdcore and the gold atoms were located around the Pdcore to produce the PdcoreAushell smlcture. 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 AumPd and AumPd2 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 O2. H2, and CO, is higher than that of the pure gold clusters.