用微正则方法从瞬子理论得到速率常数
Rate constants from instanton theory via a microcanonical approach
摘要：
微正则瞬子理论提供了在整个温度范围内提供包括原子量子隧穿在内的化学反应速率常数的希望。我们讨论了不同的速率表达式，这需要计算的瞬子的稳定性参数。传统的方法获得这些稳定性参数被证明是数值不稳定的实际应用中。我们提供了三种可供选择的算法来获得这样的稳定性参数的不可分系统，即，系统中的振动模式垂直于瞬子路径耦合沿路径的运动。我们显示了我们的算法的适用性上两个分子系统：H $_2$ + OH $\rightarrow$ H $_2$ O + H使用一个拟合的势能面和HNCO + H $\rightarrow$ NH $_2$ CO使用一个潜在的飞行从密度泛函计算。
英文摘要：
Microcanonical instanton theory offers the promise of providing rate constants for chemical reactions including quantum tunneling of atoms over the whole temperature range. We discuss different rate expressions, which require the calculation of stability parameters of the instantons. The traditional way of obtaining these stability parameters is shown to be numerically unstable in practical applications. We provide three alternative algorithms to obtain such stability parameters for non-separable systems, i.e., systems in which the vibrational modes perpendicular to the instanton path couple to movement along the path. We show the applicability of our algorithms on two molecular systems: H$_2$ + OH $\rightarrow$ H$_2$O + H using a fitted potential energy surface and HNCO + H $\rightarrow$ NH$_2$CO using a potential obtained on-the-fly from density functional calculations.
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