分子内对称性自适应微扰理论中人工多极子的克服
Overcoming Artificial Multipoles in Intramolecular Symmetry-Adapted Perturbation Theory
摘要：
分子内自适应微扰理论（ISAPT）是一种计算和分解两个分子片段A和B之间通过连接子C连接的非共价相互作用能的方法。现有的ISAPT算法显示了许多碎片模式的几个问题，包括人为排斥静电能（即使当碎片是氢键）和非常大的和相互抵消的感应和交换感应项。我们将这些问题归因于碎片间边界的人工偶极矩，因为直接连接到C的A和B的原子在它们的一个混合轨道上缺少电子。因此，我们提出了几个新的分配算法，重新分配一个电子，在一个单一的占领链接杂化轨道，从C到每个A/B。一旦将这些连接轨道的贡献加到碎片密度矩阵中，ISAPT静电能、感应能和色散能的计算就完全正常进行，交换能的表达式只需要做微小的修改。在介绍的链接分割算法，ISAPT（SIAO 1）的方法（其中链接轨道是通过投影到一个给定的片段的固有原子轨道，然后正交化到这个片段的占用空间）导致所有ISAPT校正的所有碎片模式的合理值，并表现出快速和系统的基集收敛。这种改进是通过在碎片间边界处的非物理偶极矩的幅度显著减小（即使不是完全消除）而实现的。我们证明了效用的改进ISAPT分区通过检查分子内的相互作用在几个戊二醇异构体，直链和支链烷烃的例子，和一个家庭的N-芳基亚胺分子扭秤的开放和封闭的构象。
英文摘要：
Intramolecular symmetry-adapted perturbation theory (ISAPT) is a method to compute and decompose the noncovalent interaction energy between two molecular fragments A and B connected via a linker C. The existing ISAPT algorithm displays several issues for many fragmentation patterns, including an artificially repulsive electrostatic energy (even when the fragments are hydrogen-bonded) and very large and mutually cancelling induction and exchange-induction terms. We attribute those issues to the artificial dipole moments at the interfragment boundary, as the atoms of A and B directly connected to C are missing electrons on one of their hybrid orbitals. Therefore, we propose several new partitioning algorithms which reassign one electron, on a singly occupied link hybrid orbital, from C to each of A/B. Once the contributions from these link orbitals are added to fragment density matrices, the computation of ISAPT electrostatic, induction, and dispersion energies proceeds exactly as normal, and the exchange energy expressions need only minor modifications. Among the link partitioning algorithms introduced, the ISAPT(SIAO1) approach (in which the link orbital is obtained by a projection onto the intrinsic atomic orbitals of a given fragment followed by orthogonalization to this fragment's occupied space) leads to reasonable values of all ISAPT corrections for all fragmentation patterns and exhibits fast and systematic basis set convergence. This improvement is made possible by a significant reduction in magnitude (even though not a complete elimination) of the unphysical dipole moments at the interfragment boundaries. We demonstrate the utility of the improved ISAPT partitioning by examining intramolecular interactions in several pentanediol isomers, examples of linear and branched alkanes, and the open and closed conformations of a family of N-arylimide molecular torsion balances.
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