【摘要】 利用从头算MP2方法和密度泛函理论B3LYP和B3PW91方法,研究了杂硼原子簇XB+6(X=C,Si,Ge,Sn,Pb)的结构、稳定性及化学键合情况.对C,Si,Ge,B使用6-311+G(d)基组,对Sn和Pb使用LANL2DZ赝势基组.研究结果表明,具有Cs对称性的假平面XB+6(X=C,Si,Ge,Sn,Pb)结构是势能面上的全域极小点,其稳定性要高于C6v对称性的锥形结构和C2对称性的假锥形结构.在B3LYP水平上,对这些异构体的势能面的极小点进行了自然键轨道(NBO)的分析;对最稳定构型的最高占据分子轨道(HOMO)和最低空轨道(LUMO)能级差、分子轨道(MO)和核独立化学位移(NICS)进行了计算和讨论.分析了杂原子和硼原子间、相邻硼原子间的键合情况,讨论了最稳定构型的芳香性质.更多还原

【Abstract】 The geometries, stability and chemical bonding of XB+ 6(X=C, Si, Ge, Sn, Pb) clusters were investigated using ab initio (MP2) and density functional theory (DFT: B3LYP and B3PW91) methods. Analytical gradients with polarized split-valence basis sets (6-311+G(d)) were used for B, C, Si, and Ge. The relativistic effective core potential with the LANL2DZ basis sets were chosen for Sn and Pb. The results show that the Cs symmetric pseudo-planar XB+ 6(X=C, Si, Ge, Sn, Pb) structures are the global minima on the potential energy surfaces, which are more stable than the C6v symmetric pyramidal and C2 symmetric quasi-pyramidal structures. We carried out a natural bond orbital (NBO) analysis of all these minima at the B3LYP level, and calculated and discussed the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps, the molecular orbitals (MO), and the nucleus-independent chemical shifts (NICS) of the most stable structure. The nature of the X―B and B=B bonds in these minimum structures and the aromatic characteristics (σ and π) of the most stable configuration were analyzed at the B3LYP level.更多还原