Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
J Chem Phys. 2014 Feb 14;140(6):064103. doi: 10.1063/1.4863919.
We extend ring-polymer molecular dynamics (RPMD) to allow for the direct simulation of general, electronically non-adiabatic chemical processes. The kinetically constrained (KC) RPMD method uses the imaginary-time path-integral representation in the set of nuclear coordinates and electronic states to provide continuous equations of motion that describe the quantized, electronically non-adiabatic dynamics of the system. KC-RPMD preserves the favorable properties of the usual RPMD formulation in the position representation, including rigorous detailed balance, time-reversal symmetry, and invariance of reaction rate calculations to the choice of dividing surface. However, the new method overcomes significant shortcomings of position-representation RPMD by enabling the description of non-adiabatic transitions between states associated with general, many-electron wavefunctions and by accurately describing deep-tunneling processes across asymmetric barriers. We demonstrate that KC-RPMD yields excellent numerical results for a range of model systems, including a simple avoided-crossing reaction and condensed-phase electron-transfer reactions across multiple regimes for the electronic coupling and thermodynamic driving force.
我们将环聚合物分子动力学（RPMD）扩展到允许直接模拟一般的、电子非绝热化学过程。动力学约束（KC）RPMD 方法使用核坐标和电子态的虚时路径积分表示来提供连续的运动方程，这些方程描述了系统的量子化、电子非绝热动力学。KC-RPMD 保留了通常 RPMD 构形在位置表示中的有利性质，包括严格的详细平衡、时间反演对称性以及反应速率计算对分界面选择的不变性。然而，新方法通过能够描述与一般多电子波函数相关的状态之间的非绝热跃迁，以及通过准确地描述跨越不对称势垒的深隧过程，克服了位置表示 RPMD 的显著缺点。我们证明了 KC-RPMD 对一系列模型系统都能得到很好的数值结果，包括一个简单的避免交叉反应和在电子耦合和热力学驱动力的多个区域的凝聚相电子转移反应。
