Solvent exchange in liquid methanol and rate theory

Highlights: • The TST, the IMM, the RF approaches and GH theory are used to compute rate constants. • Solvent coupling was found to dominate, resulting in a small transmission coefficient. • We predict a positive activation volume for the methanol exchange process. • The dynamics features and pressure dependence are recovered from a GLE description. To enhance our understanding of the solvent exchange mechanism in liquid methanol, we report a systematic study using molecular dynamics simulations. We use transition state theory, the Impey–Madden–McDonald method, the reactive flux method, and Grote–Hynes theory to compute the rate constants for this process. Solvent coupling was found to dominate, resulting in a significantly small transmission coefficient. We predict a positive activation volume for methanol exchange. The essential features of the dynamics as well as the pressure dependence are recovered from a Generalized Langevin Equation description of the dynamics. We find that the response to anharmonicity can be decomposed into two time regimes, one corresponding to short time response (5 ps). An effective characterization of the process is obtained from launching dynamics from the planar hypersurface corresponding to Grote–Hynes theory, resulting in improved numerical convergence of correlation functions.