Assessing parameters for ring polymer molecular dynamics simulations at low temperatures: DH + H chemical reaction

Abstract

Ring polymer molecular dynamics (RPMD) is an accurate method for calculating thermal chemical reaction rates. It has recently been discovered that low-temperature calculations are strongly affected by the simulation parameters. Here, for the thermally activated reaction DH + H → D + H2, we calculate the RPMD rate constants at T=50, 100, and 300 K and demonstrate that for T≥100 K the standard input parameters yield accurate results, but at low temperatures (e.g., 50 K) one must increase the asymptotic distance and force constant, and decrease the umbrella integration step.