On the Quantum Nature of the Shared Proton in Hydrogen Bonds
Mark E. Tuckerman,
Dominik Marx,
Michael
L. Klein,
Michele Parrinello
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.
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 für
Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart,
Germany.