接近和高于交叉温度的瞬子速率常数计算
Instanton Rate Constant Calculations Close to and Above the Crossover Temperature
摘要：
已知正则瞬子理论高估了接近系统相关交叉温度的速率常数，并且在该温度以上不适用。我们比较的准确性反应速率常数计算使用最近的半经典速率表达式从规范的瞬子理论。我们表明，纯粹从解决的稳定性矩阵的行动在自由度的瞬子路径正交计算的速率常数是不适用于在任意低的温度，并采用两种方法来克服这一点。此外，作为一个副产品的开发方法，我们得到一个简单的校正规范瞬子理论，可以减轻这种已知的高估接近交叉温度的速率常数。组合方法准确地再现了正则理论的速率常数沿整个温度范围内没有虚假的高估附近的交叉温度。计算并比较了三种不同反应的速率常数：H在Müller-Brown势中的反应，甲基羟基卡宾$\to$乙醛的反应和H $_2$ + OH $\to$ H + H $_2$ O的反应.
英文摘要：
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 employ 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 $\to$ acetaldehyde and H$_2$ + OH $\to$ H + H$_2$O.
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