PNNL

Abstract

Proton transfer in water and other solvents is a complicated process and an active research area. Conformational changes of water hydrating a proton can have a significant influence on proton dynamics. A hydrated proton leads to H3O+ that forms three hydrogen bonds with neighboring water molecules. In this letter, we report the first computer simulation of the dynamics of water exchanging between the first and second solvation shells of H3O+. Employing different rate theories for chemical reactions such as the transition state theory, the Grote-Hynes theory, the reactive flux method, and the Impey-Madden-McDonald method, we calculate the solvent exchange rates from molecular dynamics simulations that account for explicit polarization effects. In addition, we also study water exchanges around OH- and find that the corresponding time scale (~50 picoseconds [ps]) is much smaller than that for H3O+ (~100 ps). Results from all the rate theories are computed and compared. This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. The calculations were carried out using computer resources provided by the Office of Basic Energy Sciences.