Quantum-mechanical reaction rate constants from centroid molecular dynamics simulations

It has been shown recently that in order for real-time correlation function s obtained from centroid molecular dynamics (CMD) simulations to be directl y related, without further approximations, to the corresponding quantum cor relation functions, one of the operators should be linear in the position a nd/or momentum [Jang and Voth, J. Chem. Phys. 111, 2357 (1999)]. Standard r eaction rate theory relates the rate constant to the flux-Heaviside or the flux-flux correlation functions, which involve two nonlinear operators and therefore cannot be calculated via CMD without further approximations. We p resent an alternative, and completely equivalent, reaction rate theory whic h is based on the position-flux correlation function. The new formalism ope ns the door to more rigorously using CMD for the calculation of quantum rea ction rate constants in general many-body systems. The new method is tested on a system consisting of a double-well potential bilinearly coupled to a harmonic bath. The results obtained via CMD are found to be in good agreeme nt with the numerically exact results for a wide range of frictions and tem peratures. (C) 2001 American Institute of Physics.