Chen De-Li, Tian Wei Quan, Lu Wen-Cai, Sun Chia-Chung
State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, China.
J Chem Phys. 2006 Apr 21;124(15):154313. doi: 10.1063/1.2189224.
The electronic structures and stabilities of cationic MPb12+ clusters (M = B, Al, Ga, In, and Tl) with 50 valence electrons are investigated within density functional theory. It is shown that, at the B3LYP/cc-pVDZ(-PP) and BPW91/cc-pVDZ(-PP) levels of theory, the structures of MPb12+ with icosahedra (I(h)) symmetry are energetically favorable, and their high stabilities may arise from the closed-shell nature of the pi subsystems which are subject to the 2(N(pi + 1)2 rule with N(pi = 1). In addition, the possessing of large nucleus-independent chemical shifts of the five kinds of clusters reflects the common aromatic character of these clusters. From the comparison of our studies on the binding energies and the highest occupied molecular orbital and the lowest unoccupied molecular orbital energy gaps, the cluster AlPb12+ has higher stability than the others and this is consistent with the recent mass-spectrometric discovery of Al-doped Pb(n)+ clusters, in which AlPb12+ is highly abundant. The same methods are used to search for the structures of the neutral MPb12 clusters. The calculations reveal that the most stable geometries of the BPb12 and GaPb12 clusters have I(h) symmetry, the AlPb12 and InPb12 clusters have T(h) symmetry, and the TlPb12 cluster has C5v symmetry. Furthermore, the vertical ionization potentials of the neutral MPb12 clusters are smaller than that of some alkali atoms, indicating that the neutral MPb12 clusters possess superalkali character.
采用密度泛函理论研究了具有50个价电子的阳离子MPb12+团簇（M = B、Al、Ga、In和Tl）的电子结构和稳定性。结果表明，在B3LYP/cc-pVDZ(-PP)和BPW91/cc-pVDZ(-PP)理论水平下，具有二十面体（I(h)）对称性的MPb12+结构在能量上是有利的，其高稳定性可能源于π子系统的闭壳层性质，该子系统遵循2(N(π + 1)2规则，其中N(π = 1)。此外，这五种团簇具有较大的核独立化学位移，反映了这些团簇共同的芳香性。通过对结合能、最高占据分子轨道和最低未占据分子轨道能隙的研究比较，发现团簇AlPb12+比其他团簇具有更高的稳定性，这与最近质谱研究中发现的掺铝Pb(n)+团簇一致，其中AlPb12+含量很高。采用相同的方法搜索中性MPb12团簇的结构。计算结果表明，BPb12和GaPb12团簇最稳定的几何结构具有I(h)对称性，AlPb12和InPb12团簇具有T(h)对称性，TlPb12团簇具有C5v对称性。此外，中性MPb12团簇的垂直电离势小于一些碱金属原子，表明中性MPb12团簇具有超碱性质。
