Structural change in D2O water as a function of temperature: the isochoric temperature derivative function for neutron diffraction

Neutron diffraction measurements have been made for liquid D2O water at four temperatures covering the normal and super-cooled phases. Pairs of temperatures have been chosen where the density is equivalent, either side of the density maximum. A temperature difference technique is used to extract the change in the structure factor as a function of temperature and this function is transformed to give the change in the composite spatial correlation function. It is shown that there is a systematic variation in the structure which extends over a range up to 10 Angstrom and above. The changes can be correlated with the network structure of low-density amorphous ice and these features emphasise the extended range of the hydrogen-bond connectivity in the liquid phase.