Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
J Chem Phys. 2018 Mar 14;148(10):102327. doi: 10.1063/1.5005544.
We describe a path-integral approach for including nuclear quantum effects in non-adiabatic chemical dynamics simulations. For a general physical system with multiple electronic energy levels, a corresponding isomorphic Hamiltonian is introduced such that Boltzmann sampling of the isomorphic Hamiltonian with classical nuclear degrees of freedom yields the exact quantum Boltzmann distribution for the original physical system. In the limit of a single electronic energy level, the isomorphic Hamiltonian reduces to the familiar cases of either ring polymer molecular dynamics (RPMD) or centroid molecular dynamics Hamiltonians, depending on the implementation. An advantage of the isomorphic Hamiltonian is that it can easily be combined with existing mixed quantum-classical dynamics methods, such as surface hopping or Ehrenfest dynamics, to enable the simulation of electronically non-adiabatic processes with nuclear quantum effects. We present numerical applications of the isomorphic Hamiltonian to model two- and three-level systems, with encouraging results that include improvement upon a previously reported combination of RPMD with surface hopping in the deep-tunneling regime.
我们描述了一种在非绝热化学动力学模拟中包含核量子效应的路径积分方法。对于具有多个电子能级的一般物理系统，引入了相应的同构哈密顿量，使得通过经典核自由度对同构哈密顿量进行玻尔兹曼抽样，可以得到原始物理系统的精确量子玻尔兹曼分布。在单个电子能级的极限下，同构哈密顿量简化为熟悉的环聚合物分子动力学（RPMD）或质心分子动力学哈密顿量，具体取决于实现方式。同构哈密顿量的一个优点是它可以很容易地与现有的混合量子经典动力学方法（如表面跳跃或 Ehrenfest 动力学）结合使用，从而能够模拟具有核量子效应的电子非绝热过程。我们对同构哈密顿量进行了数值应用，以模拟二能级和三能级系统，得到了令人鼓舞的结果，包括在深隧穿区域中改进了 RPMD 与表面跳跃的先前报道的组合。
