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

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.

Automated summary

Ring polymer molecular dynamics (RPMD) is an accurate method for calculating thermal chemical reaction rates. It was found that simulation parameters strongly affect low-temperature calculations, and adjustments are needed to improve accuracy at low temperatures.