Gao Jiali, Cembran Alessandro, Mo Yirong
Department of Chemistry, Digital Technology Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455, and Department of Chemistry, Western Michigan University, Kalamazoo, Michigan 49008.
J Chem Theory Comput. 2010 Aug 10;6(8):2402-10. doi: 10.1021/ct100292g.
The mixed molecular orbital and valence bond (MOVB) method has been used to generalize the explicit polarization (X-Pol) potential to incorporate charge delocalization resonance effects in the framework of valence bond theory. In the original X-Pol method, a macromolecular system is partitioned into individual fragments or blocks, and the molecular orbitals of the system are strictly localized within each block. Consequently, these block-localized molecular orbitals (BLMOs) are nonorthogonal across different blocks. In the generalized X-Pol (GX-Pol) theory, we construct charge delocalization VB states by expanding the localization space from monomer blocks into pairwise delocalized blocks. Thus, the expansion of the basis space leads to charge delocalization between monomer pairs, and a series of pairwise delocalization states can be constructed. In general, L-body delocalized states can be analogously defined by grouping L monomer blocks into one. The Hartree product wave function for each state can be fully antisymmetrized, which introduces explicitly exchange repulsion among all blocks. The GX-Pol wave function is a linear combination of all L-body charge transfer (valence bond) states, which incorporates charge delocalization and their resonance as well as static correlation effects. The GX-Pol method provides a general and rigorous theory to incorporate charge delocalization explicitly into these fragment-based electronic structural methods for macromolecular systems.
混合分子轨道与价键（MOVB）方法已被用于推广显式极化（X-Pol）势，以便在价键理论框架内纳入电荷离域共振效应。在原始的X-Pol方法中，一个大分子系统被划分为单个片段或块，并且系统的分子轨道严格定域在每个块内。因此，这些块定域分子轨道（BLMOs）在不同块之间是非正交的。在广义X-Pol（GX-Pol）理论中，我们通过将定域空间从单体块扩展到成对离域块来构建电荷离域价键态。因此，基空间的扩展导致单体对之间的电荷离域，并且可以构建一系列成对离域态。一般来说，L体离域态可以通过将L个单体块组合成一个类似地定义。每个态的哈特里积波函数可以完全反对称化，这在所有块之间明确引入了交换排斥。GX-Pol波函数是所有L体电荷转移（价键）态的线性组合，它纳入了电荷离域及其共振以及静态相关效应。GX-Pol方法提供了一种通用且严格的理论，用于将电荷离域明确纳入这些基于片段的大分子系统电子结构方法中。
