Structural H/D isotope effect in excess proton/deuteron in light/heavy water solvent by using path integral molecular dynamics simulation

Abstract We have analyzed the structural H/D isotope effect between an excess proton in light water (H-body) and an excess deuteron in heavy water (D-body), including the nuclear quantum effect by path integral molecular dynamics simulation. We found that the second peak of the H-body is shorter than that of the D-body in the radial distribution function of O*–O, where O* is the oxygen atom of H3O+/D3O+ fragment. The main reason for this would be the difference in the ratio of the Zundel structure with the sp3-like configuration, where the Zundel structure in H-body (14.0%) is greater than that in D-body (12.0%). We also found rare occurrences of double H3O+/D3O+ configurations, mainly including the Zundel-Zundel-like structures such as H7O3+/D7O3+ and H9O4+/D9O4+. The ratios of such configurations appearing in our simulations are 0.89% and 0.20% for the H-body and D-body, respectively.