作为一类不符合八隅律的超价化合物，多卤阴离子体系中化学键本质的研究对于丰富化学键理论有着重要的意义。最近，新颖的多卤阴离子体系不断地被合成和表征，其组成和结构也越发的丰富和复杂。然而多卤阴离子的理论研究大多专注于小尺寸简单体系，适用于复杂体系的化学键理论模型仍有待完善。在本项目中我们将综合地应用块定域化波函数(Block-Localized Wavefunction, BLW)方法、基于BLW方法的能量分解方法、AIM理论和静电势能分析、电子密度差分图、势能面分析等先进的计算化学方法和分析手段，对多卤阴离子的几何构型特征、稳定性和协同/反协同效应进行全面的研究，以期对其中化学键的本质有新的了解。同时，我们将探究多卤阴离子内结构单元之间及其聚合物中多卤阴离子之间化学键的主导因素和本质，并比较分析不同价态、元素组成对体系的影响，从而系统地发展和完善适用于复杂多卤阴离子体系的化学键理论模型。

In recent years, experimental investigation of polyhaolge anions becomes a focus of chemistry, and many novel systems have been discovered. As a kind of hypervalent compound which violates the octet rule, polyhalogen anions challenge the simple models of chemical bonding theory and therefore have attracted great interests of theoretical chemists. However, most of the theoretical investigations focused on the nature of chemical bond in polyhalogen anions with small sizes, leaving the recently synthesized cases less explored. In this project, the key structural parameters, stability and cooperative effect of polyhalogen anions will be investigated comprehensively using the Block-localized wavefunction (BLW) method and other novel computational chemical methods. The nature of chemical bonds in and between polyhalogen anions will be explored by analyzing the electrostatic energy surfaces of basic building blocks, the electron density variation upon formation of complex, the topology of electron density and the importance of each energy component calculated using the energy decomposition approach based on BLW method (BLW-ED). Most importantly, a coherent theoretical model of the chemical bonds in polyhalogen anions with different sizes, chemical compositions and valences will be proposed, by analyzing the similarities and differences among all cases.