Beijing National Laboratory for Molecular Sciences, Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
J Chem Phys. 2018 Mar 14;148(10):102319. doi: 10.1063/1.5005059.
An exact approach to compute physical properties for general multi-electronic-state (MES) systems in thermal equilibrium is presented. The approach is extended from our recent progress on path integral molecular dynamics (PIMD), Liu et al. [J. Chem. Phys. 145, 024103 (2016)] and Zhang et al. [J. Chem. Phys. 147, 034109 (2017)], for quantum statistical mechanics when a single potential energy surface is involved. We first define an effective potential function that is numerically favorable for MES-PIMD and then derive corresponding estimators in MES-PIMD for evaluating various physical properties. Its application to several representative one-dimensional and multi-dimensional models demonstrates that MES-PIMD in principle offers a practical tool in either of the diabatic and adiabatic representations for studying exact quantum statistics of complex/large MES systems when the Born-Oppenheimer approximation, Condon approximation, and harmonic bath approximation are broken.
本文提出了一种精确计算多电子态（MES）体系在热平衡下物理性质的方法。该方法是从我们最近在路径积分分子动力学（PIMD）方面的进展[J. Chem. Phys. 145, 024103 (2016)]和 Zhang 等人的工作[J. Chem. Phys. 147, 034109 (2017)]扩展而来的，适用于涉及单个势能面时的量子统计力学。我们首先定义了一个有效的势能函数，该函数在 MES-PIMD 中数值上是有利的，然后在 MES-PIMD 中推导出了用于评估各种物理性质的相应估计量。它在几个有代表性的一维和多维模型中的应用表明，当玻恩-奥本海默近似、康顿近似和调和浴近似被打破时，MES-PIMD 原则上为研究复杂/大型 MES 体系的精确量子统计提供了一种实用工具，无论是在绝热表示还是非绝热表示中。
