CLASSICAL AND QUANTUM CHEMICAL RATE CONSTANTS FOR REACTIONS IN CONDENSED PHASES

Abstract

Methods for the computation of rate constants that characterize quantum and classical reactions occurring in the condensed phase are discussed. While expressions for these transport properties are well known, their computation presents challenges for simulation since reactive events often occur rarely, and the long time scales that are typical for reactive processes are not accessible using simple molecular dynamics methods. Furthermore, the reaction coordinate in a condensed phase system may be a complex many-body function of the system's degrees of freedom. The study of chemical rate processes in quantum mechanical systems presents additional challenges. Except for systems with few degrees of freedom, such quantum rate processes cannot be simulated because of the difficulties in solving the time dependent Schrodinger equation for a condensed phase system. For situations where a quantum rate process takes place in an environment that may be treated classically to a good approximation, mixed quantum-classical approaches provide a route to study such systems. Some of the issues that arise in the theoretical description and computer simulation of rare classical and quantum reactive events are discussed in this paper. [Chem. Educ. Res. Pract. Eur., 2002, 3, 253- 268]