线性碳元素簇合物的成键性质

THE BONDING PROPERTIES FOR LINEAR CARBON ELEMENT CLUSTERS

在ab initio 3-21G 水平上,用能量梯度法优化了线性碳元素簇合物C_n^e(n 为成簇原子个数,e 为电荷)的平衡几何结构.所得的电离势随成簇原子个数的改变,呈现出不同程度的奇偶交替变化趋势.在ab initio 计算基础上,用Boys 方法,对其占据正则分子轨道进行定域化变换,得到了它们的定域分子轨道.对定域分子轨道性质的分析表明,线性碳元素簇合物中,主要键型有双中心σ和π健,双中心弯键和三中心香蕉健,以及多中心σ和π健.这种键型的多样化可视为小元素簇的成健特征.此外,通过对其成键性质的分析,讨论了线性碳元素簇的稳定性.对于小碳元素簇,化学键的共轭性对其稳定性具有十分显著的作用.

At the level of ab initio 3-21G,the equilibrum geometries of linear carbon clusters C_n^e(n≤8,|e|≤2)have been optimized by using an energy gradient method.Ionization potentials ob-tained display odd-even alternations with the increase of carbon atoms in clusters.Based onab initio calculations,occupied canonical molecular orbitals(CMO)are localized with Boys local-ization method.Analysis of the properties of LMOs shows that there are two-centre σ and π bonds,multi-centre σ and π bonds and bending bonds in the linear carbon clusters C_n^e.Such as this va-riety of bonding types could be considered as the character of bonding behavior for small carbonclusters.Furthermore,the relations between bonding properties and stabilities are discussed.Itis shown that the conjugation of chemical bonds plays a significant role for the stabilities of smallcarbon element clusters.