Tunneling splittings from path-integral molecular dynamics using a Langevin thermostat.
Tunneling splittings from path-integral molecular dynamics using a Langevin thermostat.
复制标题
DOI：
10.1063/1.5029258
复制
发表时间：
2018-03
期刊：
影响因子：
--
通讯作者：
C. L. Vaillant;D. Wales;S. Althorpe
中科院分区：
文献类型：
--
作者：
C. L. Vaillant;D. Wales;S. Althorpe
我们报告了一种使用路径积分分子动力学（PIMD）计算分子和簇中简并构型之间的隧道分裂的改进方法。从涉及对称井底部热力学密度矩阵比率的表达式开始，我们使用热力学积分与分子动力学模拟和朗之万恒温器来随机计算分裂。热力学积分是通过沿着半经典瞬子路径采样来执行的，这提供了有效的反应坐标并且具有良好的物理动机。这种方法使我们能够对水二聚体中的多井隧道分裂模式进行 PIMD 计算，并改进之前针对一维模型和丙二醛的 PIMD 计算。水二聚体中的大（受体）分裂在基准变异结果的 20% 以内一致，较小的分裂在 10% 以内一致。
We report an improved method for the calculation of tunneling splittings between degenerate configurations in molecules and clusters using path-integral molecular dynamics (PIMD). Starting from an expression involving a ratio of thermodynamic density matrices at the bottom of the symmetric wells, we use thermodynamic integration with molecular dynamics simulations and a Langevin thermostat to compute the splittings stochastically. The thermodynamic integration is performed by sampling along the semiclassical instanton path, which provides an efficient reaction coordinate as well as being physically well-motivated. This approach allows us to carry out PIMD calculations of the multi-well tunneling splitting pattern in the water dimer and to refine previous PIMD calculations for one-dimensional models and malonaldehyde. The large (acceptor) splitting in the water dimer agrees to within 20% of benchmark variational results, and the smaller splittings agree to within 10%.