Quantum Free Energy Profiles for Molecular Proton Transfers

Although many molecular dynamics simulations treat the atomic nuclei as classical particles, an adequate description of nuclear quantum effects (NQEs) is indispensable when studying proton transfer reactions. Herein, quantum free energy profiles are constructed for three typical proton transfers, which properly take NQEs into account using the path integral formalism. The computational cost of the simulations is kept tractable by deriving machine learning potentials. It is shown that the classical and quasi-classical centroid free energy profiles of the proton transfers deviate substantially from the exact quantum free energy profile.

Automated summary

Although many molecular dynamics simulations treat atomic nuclei as classical particles, it is necessary to consider nuclear quantum effects (NQEs) when studying proton transfer reactions. In this study, quantum free energy profiles for three typical proton transfers, which properly include NQEs using the path integral formalism, are constructed. The computational cost of the simulations is reduced by using machine learning potentials. The results show a significant deviation between classical/quasi-classical centroid free energy profiles and the exact quantum free energy profile for proton transfers.