McConnell Sean, Kästner Johannes
Institute for Theoretical Chemistry, University of Stuttgart, Pfaffenwaldring 55, Stuttgart, 70569, Germany.
J Comput Chem. 2017 Nov 15;38(30):2570-2580. doi: 10.1002/jcc.24914. Epub 2017 Aug 19.
Canonical instanton theory is known to overestimate the rate constant close to a system-dependent crossover temperature and is inapplicable above that temperature. We compare the accuracy of the reaction rate constants calculated using recent semi-classical rate expressions to those from canonical instanton theory. We show that rate constants calculated purely from solving the stability matrix for the action in degrees of freedom orthogonal to the instanton path is not applicable at arbitrarily low temperatures and use two methods to overcome this. Furthermore, as a by-product of the developed methods, we derive a simple correction to canonical instanton theory that can alleviate this known overestimation of rate constants close to the crossover temperature. The combined methods accurately reproduce the rate constants of the canonical theory along the whole temperature range without the spurious overestimation near the crossover temperature. We calculate and compare rate constants on three different reactions: H in the Müller-Brown potential, methylhydroxycarbene → acetaldehyde and H + OH → H + H O. © 2017 Wiley Periodicals, Inc.
已知正则瞬子理论在接近一个与系统相关的交叉温度时会高估速率常数，并且在该温度以上不适用。我们将使用最近的半经典速率表达式计算得到的反应速率常数的准确性与正则瞬子理论计算得到的准确性进行比较。我们表明，仅通过求解与瞬子路径正交的自由度下作用量的稳定性矩阵来计算速率常数，在任意低温下都不适用，并使用两种方法来克服这一问题。此外，作为所开发方法的一个副产品，我们推导出了对正则瞬子理论的一个简单修正，该修正可以缓解在接近交叉温度时已知的速率常数高估问题。这些组合方法在整个温度范围内准确地再现了正则理论的速率常数，而不会在交叉温度附近出现虚假的高估。我们计算并比较了三个不同反应的速率常数：处于穆勒 - 布朗势中的氢原子、甲基羟基卡宾→乙醛以及H + OH→H + H₂O。© 2017威利期刊公司。
