title: On the Quantum Nature of the Shared Proton in Hydrogen Bonds
abstract: The relative influence of thermal and quantum fluctuations on the proton transfer properties of the charged water complexes H5O2+ and H3O2- was investigated with the use of ab initio techniques. These small systems can be considered as prototypical representatives of strong and intermediate-strength hydrogen bonds. The shared proton in the strongly hydrogen bonded H5O2+ behaved in an essentially classical manner, whereas in the H3O2- low-barrier hydrogen bond, quantum zero-point motion played a crucial role even at room temperature. This behavior can be traced back to a small difference in the oxygen-oxygen separation and hence to the strength of the hydrogen bond.
authors.affiliation: M. E. Tuckerman and M. L. Klein, Center for Molecular Modeling and Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA. D. Marx and M. Parrinello, Max-Planck-Institut fur Festkorperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.initials: ME
authors.lastname: Tuckerman
authors.initials: D
authors.lastname: Marx
authors.initials: ML
authors.lastname: Klein
authors.initials: M
authors.lastname: Parrinello