用局部李雅普诺夫偏置的过渡路径采样法计算反应常数
Calculation of reaction constants using Transition Path Sampling with a local Lyapunov bias
摘要：
提出了一种计算有限温度下多体系统热激活过程反应速率常数的有效方法。该方法包括两个步骤：第一，使用过渡路径采样（TPS）算法补充有利于发散轨迹的局部李雅普诺夫偏置路径进行采样。这提高了在相对较短的模拟期间观察到稳定状态之间的罕见反应轨迹的概率。其次，反应常数最终估计从反应路径的无偏分数，产生了一个适当的统计数据分析工具，多态贝内特验收比（MBAR）包。为了测试我们的算法，我们计算LJ 38，一个很好的研究Lennard-Jones集群的结构转变的反应常数，比较我们的结果，以前在文献中报道的值。此外，我们还将此方法应用于300 ~ 850 K温度范围内α-Fe晶体中空位迁移的反应速率的计算。空位扩散率与激活势垒在有限的温度下，然后评估，并使用标准谐波近似得到的值进行比较。
英文摘要：
We propose an efficient method to compute reaction rate constants of thermally activated processes occurring in many-body systems at finite temperature. The method consists in two steps: first, paths are sampled using a transition path sampling (TPS) algorithm supplemented with a local Lyapunov bias favoring diverging trajectories. This enhances the probability of observing rare reactive trajectories between stable states during relatively short simulations. Secondly, reaction constants are eventually estimated from the unbiased fraction of reactive paths, yielded by an appropriate statistical data analysis tool, the multistate Bennett acceptance ratio (MBAR) package. In order to test our algorithm, we compute reaction constants for structural transitions in LJ38, a well studied Lennard-Jones cluster, comparing our results to values previously reported in the literature. Additionally, we apply our method to the calculation of reaction rates for vacancy migration in an α-Iron crystal, for temperatures ranging from 300 K to 850 K. Vacancy diffusion rates associated with activation barriers at finite temperature are then evaluated, and compared to values obtained using the standard harmonic approximation.
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