The local bonding in water from -20 to 220 degrees C

It is believed that the mean distance between water molecules increases with a decrease in water temperature below room temperature due to the increase in 'hydrogen bonds', which implies an increase in the local fourfold coordination. In order to investigate how far this effect extends over a wider range, we have made constant-density measurements of the principal peak of the neutron structure factor of heavy water as a function of temperature. Data were taken at densities from 10% greater to 8% less than the maximum density at 1 atm, and for temperatures extending from -20 to 220 degrees C. The effects seen at ambient conditions were found to extend over this whole range.