铌团簇和配合物的多面体分子轨道理论研究

Polyhedral Molecular Orbital Theory to Niobium Clusters and Metal Complex

应用多面体理论方法研究铌纯金属团簇和配合物的电子结构成键性质,并将理论预测结果用密度泛函方法验证.证实多面体理论是简便预测过渡金属簇,尤其是簇骨架电子结构的有效方法.铌的小团簇总是以低自旋密堆积结构为稳定构型,当体系的价电子数满足轨道成键数时,用该方法可较准确地推断成键性质(如Nb4和[Nb6Cl12]+4);而对于不满足成键数的体系(如Nb5和Nb6),则可利用该理论分析畸变趋势.

The polyhedral molecular orbital method was applied to several niobium clusters, and a model of standard trigonometric integral was used in order to simplify the calculation of group overlap integrals. Furthermore, the results were checked by the density functional theory. The comparisons show that the polyhedral molecular orbital theory is a more efficient way for studying the bond characters of polyhedral compounds, especially transition metal clusters, than the traditional calculation methods. For example, this method predicts that the sizes of niobium clusters possess low magnetic moments as ground states, and the electronic structures of Nb4 and [Nb6Cl12]^＋4. Although the geometry structures of Nb5 and Nb6 are transformed resulting from the Jahn-Teller effects and electronic-correlated effects, the theoretical prediction also show the trend of transformation.