Chemical Assignment of Symmetry-Adapted Perturbation Theory Interaction Energy Components: The Functional-Group SAPT Partition

Recently, we introduced an effective atom-pairwise partition of the many-body symmetry-adapted perturbation theory (SAPT) interaction energy decomposition, producing a method known as atomic SAPT (A-SAPT) [Parrish, R. M.; Sherrill, C. D. J. Chem. Phys. 2014, 141, 044115]. A-SAPT provides ab initio atom-pair potentials for force field development and also automatic visualizations of the spatial contributions of noncovalent interactions, but often has difficulty producing chemically useful partitions of the electrostatic energy, due to the buildup of oscillating partial charges on adjacent functional groups. In this work, we substitute chemical functional groups in place of atoms as the relevant local quasiparticles in the partition, resulting in a functional-group-pairwise partition denoted as functional-group SAPT (F-SAPT). F-SAPT assigns integral sets of local occupied electronic orbitals and protons to chemical functional groups and linking σ bonds. Link-bond contributions can be further assigned to chemical functional groups to simplify the analysis. This approach yields a SAPT partition between pairs of functional groups with integral charge (usually neutral), preventing oscillations in the electrostatic partition. F-SAPT qualitatively matches chemical intuition and the cut-and-cap fragmentation technique but additionally yields the quantitative many-body SAPT interaction energy. The conceptual simplicity, chemical utility, and computational efficiency of F-SAPT is demonstrated in the context of phenol dimer, proflavine+–DNA intercalation, and a cucurbituril host–guest inclusion complex.近期，我们提出了一种针对多体对称匹配微扰理论（many-body symmetry-adapted perturbation theory, SAPT）相互作用能分解的有效原子对划分方案，由此得到了名为原子SAPT（atomic SAPT, A-SAPT）的计算方法[Parrish, R. M.; Sherrill, C. D. J. Chem. Phys. 2014, 141, 044115]。A-SAPT可用于力场开发所需的从头算原子对势，同时还能实现非共价相互作用空间贡献的自动可视化，但由于相邻官能团上会出现振荡的部分电荷，该方法往往难以得到具有化学实用价值的静电能划分结果。 在本研究中，我们以化学官能团替代原子作为划分过程中的局域准粒子，由此得到了官能团对划分方案，即官能团SAPT（functional-group SAPT, F-SAPT）。F-SAPT将局域占据电子轨道与质子的完整集合分配给化学官能团以及连接用σ键，还可将键贡献进一步分配至对应官能团以简化分析流程。该方法实现了电荷为整数（通常为中性）的官能团对之间的SAPT划分，有效避免了静电能划分中的振荡问题。F-SAPT不仅在定性上符合化学直觉与切割-封端碎片化技术的分析逻辑，同时还能给出定量的多体SAPT相互作用能。我们通过苯酚二聚体、原黄素正离子-DNA嵌入复合物以及葫芦脲主客体包结配合物三个典型体系，验证了F-SAPT在概念简洁性、化学实用性与计算效率上的优势。