Science Institute and Faculty of Physical Sciences, University of Iceland VR-III, 107 Reykjavík, Iceland.
J Chem Phys. 2018 Mar 14;148(10):102334. doi: 10.1063/1.5007180.
Methodology for finding optimal tunneling paths and evaluating tunneling rates for atomic rearrangements is described. First, an optimal JWKB tunneling path for a system with fixed energy is obtained using a line integral extension of the nudged elastic band method. Then, a calculation of the dynamics along the path is used to determine the temperature at which it corresponds to an optimal Feynman path for thermally activated tunneling (instanton) and a harmonic approximation is used to estimate the transition rate. The method is illustrated with calculations for a modified two-dimensional Müller-Brown surface but is efficient enough to be used in combination with electronic structure calculations of the energy and atomic forces in systems containing many atoms. An example is presented where tunneling is the dominant mechanism well above room temperature as an HBNH molecule dissociates to form H. Also, a solid-state example is presented where density functional theory calculations of H atom tunneling in a Ta crystal give close agreement with experimental measurements on hydrogen diffusion over a wide range in temperature.
描述了一种用于寻找最优隧道路径和评估原子重排隧道速率的方法。首先，使用受 nudged 弹性带方法启发的线积分扩展，获得了具有固定能量的系统的最优 JWKB 隧道路径。然后，沿着该路径进行动力学计算，以确定与热激活隧道（虚粒子）的最优费曼路径对应的温度，并使用谐波近似来估计跃迁率。该方法通过对改进的二维 Müller-Brown 表面的计算进行了说明，但效率足够高，可以与包含许多原子的系统的能量和原子力的电子结构计算结合使用。本文提供了一个实例，其中在室温以上，隧道是主要的分解机制，如 HBNH 分子分解为 H。此外，还提供了一个固态实例，其中 Ta 晶体中 H 原子隧道的密度泛函理论计算与温度范围内广泛的氢扩散实验测量结果非常吻合。
