【摘要】 采用HF,B3LYP,MP2和QCISD等理论方法在6-31G和6-31G*基组水平上,对C20的3个主要异构体碟型(Bowl)、笼型(Cage)和环型(Ring)的结构进行理论研究,得出这3个异构体的相对稳定性的次序为:Ring>Bowl>Cage.计算结果显示,分子轨道具有离域特性,电子的这种离域特征有利于原子间更好的成键,可避免出现大的张力,这是Cage型异构体虽然违反“五元环隔离规则”(Isolatedpentagonrule)却能稳定存在的原因.更多还原

【Abstract】 Three isomers of C₂₀, bowl, cage, and ring, were investigated by using the HF, B3LYP, MP2, QCISD methods at 6-31G and 6-31G^* level to obtain the optimized geometries and the order of their stability was as follows: Ring >Bowl >Cage. The calculated results show that the molecular orbital has multi-center characters and the electronic delocalization is favourable for bonding between atoms and can avoid the strong tension. This is the reason that the isomer of cage can exit stably though it breaks "isolated pentagon rule".更多还原