Kowalski Piotr H, Krzemińska Agnieszka, Pernal Katarzyna, Pastorczak Ewa
Institute of Physics, Lodz University of Technology, ul. Wolczanska 217/221, 93-005 Lodz, Poland.
J Phys Chem A. 2022 Feb 24;126(7):1312-1319. doi: 10.1021/acs.jpca.2c00004. Epub 2022 Feb 15.
The London dispersion interactions between systems undergoing bond breaking, twisting, or compression are not well studied due to the scarcity and the high computational cost of methods being able to describe both the dynamic correlation and the multireference character of the system. Recently developed methods based on the Generalized Valence Bond wave function, such as EERPA-GVB and SAPT(GVB) (SAPT = symmetry-adapted perturbation theory), allow one to accurately compute and analyze noncovalent interactions between multireference systems. Here, we augment this analysis by introducing a local indicator for dispersion interactions inspired by Mata and Wuttke's Dispersion Interaction Density [ 2017, 38, 15-23] applied on top of an EERPA-GVB computation. Using a few model systems, we show what insights into the nature and evolution of the dispersion interaction during bond breaking and twisting such an approach is able to offer. The new indicator can be used at a minimal cost additional to an EERPA-GVB computation and can be complemented by an energy decomposition employing the SAPT(GVB) method. We explain the physics behind the initial increase, followed by a decrease in the interaction of linear molecules upon bond stretching. Namely, the elongation of covalent bonds leads to the enhancement of attractive dispersion interactions. For even larger bond lengths, this effect is canceled by the increase of the repulsive exchange forces resulting in a suppression of the interaction and finally leading to repulsion between monomers.
由于能够描述系统动态相关性和多参考特征的方法稀缺且计算成本高昂，对于经历键断裂、扭曲或压缩的系统之间的伦敦色散相互作用尚未得到充分研究。最近基于广义价键波函数开发的方法，如EERPA - GVB和SAPT(GVB)（SAPT = 对称适配微扰理论），使人们能够准确计算和分析多参考系统之间的非共价相互作用。在此，我们通过引入一种受Mata和Wuttke的色散相互作用密度[2017, 38, 15 - 23]启发的色散相互作用局部指标来增强这种分析，该指标应用于EERPA - GVB计算之上。使用一些模型系统，我们展示了这种方法能够为键断裂和扭曲过程中色散相互作用的性质和演化提供哪些见解。新指标在EERPA - GVB计算之外只需额外付出最小的成本即可使用，并且可以通过采用SAPT(GVB)方法的能量分解来补充。我们解释了线性分子在键拉伸时相互作用先增加后减少背后的物理原理。即，共价键的伸长导致吸引性色散相互作用增强。对于更大的键长，这种效应被排斥性交换力的增加所抵消，导致相互作用受到抑制，最终导致单体之间产生排斥。
