Isotope effects in water as investigated by neutron diffraction and path integral molecular dynamics.
The structures of heavy and  light water at 300 K were investigated by using a joint approach in which the method of neutron diffraction with oxygen isotope substitution was complemented by path integral molecular dynamics simulations. The diffraction results, which give intra-molecular O-D and O-H bond distances of 0.985(5) and 0.990(5) Å, were found to be in best agreement with those obtained by using the flexible anharmonic TTM3-F water model. Both techniques show a difference of  ≃ 0.5% between the O-D and O-H intra-molecular bond lengths, and the results support a competing quantum effects model for water in which its structural and dynamical properties are governed by an offset between intra-molecular and inter-molecular quantum contributions. Further consideration of the O-O correlations is needed in order to improve agreement with experiment.
Department of Physics, University of Bath, Bath BA2 7AY, UK.
Anita
A
Zeidler
Philip S
PS
Salmon
Henry E
HE
Fischer
Jörg C
JC
Neuefeind
J Mike
JM
Simonson
Thomas E
TE
Markland