Reaction kinetics and solvation: from computational methods to practical theories

加州大学圣巴巴拉分校的彼得斯男爵获得了化学部化学理论、模型和计算方法项目的支持，以开发简单而准确的理论来研究溶液中的化学反应。这种反应是许多自然和工业过程的核心，包括我们自己的生物化学。目前的模拟方法将溶剂视为可极化的连续体，具有严重的局限性。其他更复杂的模拟方法能够预测速度，但往往无法深入了解反应的潜在机制。在没有机械理解的情况下预测心率的能力似乎是一种优势，但这些分析并不能帮助研究人员从大规模计算过渡到简单、准确和易于理解的模型。简单的理论模型，如本项目中开发的模型；帮助科学家设计涉及复杂反应的过程。此外，简单的模型既可以预测利率，也可以解释来自实验的利率数据。拟议的工作将对化学、物理、生物学、地质学、材料科学和工程学产生潜在影响。彼得斯和他的研究小组开发了软件、文档和YouTube教程，以帮助其他人使用LAMMPS(大规模原子/分子大规模并行模拟器；桑迪亚国家实验室)、CHARMM(哈佛大分子力学化学)和其他广泛使用的软件包来执行这些分析。已经为气相反应、表面反应和电子转移反应开发的简单但准确的理论有一个共同的特点：它们建立在准确总结机理的单一反应坐标上。相比之下，溶剂反应的坐标仍然难以捉摸。彼得斯和他的同事提出了一种新的策略，使用可以应用于具有相似静电特性的反应的广泛家族的程序来构建溶剂坐标。该方法结合了连续介质溶剂化方法、变分过渡态理论、电子转移理论中的能隙坐标和新的极化进程坐标。这些坐标的相对重要性将使用过渡路径抽样和似然最大化方法来确定。这种计算分析不是直接产生速率，而是指导构建简单的速率理论，这些理论可以用于预测整个反应家族的趋势。这些结果被用来将溶液中的反应分为机械族，并开发不同反应族中平衡和非平衡溶剂化效应的实用经验规则。

Baron Peters of the University of California, Santa Barbara, is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry Division for to develop simple and accurate theories to study chemical reactions in solution. Such reactions are central to many natural and industrial processes, including our own biochemistry. Current simulation approaches that treat the solvent as a polarizable continuum have severe limitations. Other, more sophisticated simulation approaches are able to predict rates but often do not give any insight into the underlying mechanisms of the reaction. The ability to predict rates without mechanistic understanding seems like an advantage, but these analyses do not help researchers graduate from large scale computation to simple, accurate, and understandable models. Simple theoretical models, such as those developed in this project; help scientists engineer processes involving complex reactions. Moreover, simple models can both predict rates and interpret rate data from experiments. The proposed work will have potential impact on chemistry, physics, biology, geology, materials science and engineering. Peters and his research group develop software, documentation, and YouTube tutorials to help others perform these analyses with LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator; Sandia National Laboratories), CHARMM (Chemistry at HARvard Macromolecular Mechanics), and other widely used software packages. The simple but accurate theories that have been developed for gas phase reactions, surface reactions, and electron transfer reactions share one common characteristic: they are built around a single reaction coordinate which accurately summarizes the mechanism. In contrast, solvent reaction coordinates remain elusive. Peters and coworkers propose a new strategy for constructing the solvent coordinates using procedures that can be applied across broad families of reactions with similar electrostatic characteristics. The approach combines elements of continuum solvation approaches, variational transition state theory, energy gap coordinates from electron transfer theory, and a new polarization progress coordinate. The relative importance of these coordinates will be determined using transition path sampling and likelihood maximization approaches. Instead of directly generating rates, this computational analysis guides the construction of simple rate theories that can be used to predict trends across entire reaction families. These results are used to classify reactions in solution into mechanistic families and to develop practical rules-of-thumb for equilibrium and non-equilibrium solvation effects across the different reaction families.