Quantum effects and the local environment of water hydrogen: Deep inelastic neutron scattering study

Abstract

A deep inelastic neutron scattering experiment, performed on D${}_2$O in the temperature range 276–292 K provides insight on changes of the local environment of the water deuteron around the temperature of maximum density. We have measured the deuteron average kinetic energy and momentum distribution and found that their temperature dependence closely follows that shown by the density of the bulk liquid. These findings suggest an anomalous behavior of both kinetic energy and momentum distribution, similar to that observed for H${}_2$O. However, in contrast to previous results on light water, no signatures of deuteron delocalization along the hydrogen bond have been observed for supercooled D${}_2$O. This indicates a different relevance of quantum effects in the two liquids. Data such as that discussed here, are crucial to assess the validity of existing electrostatic-based models to describe changes of the water intermolecular potential upon hydrogen bonding.