Neutron diffraction studies of water

Abstract

Neutron diffraction measurements have been made for heavy water at five temperatures in the range 11–75°C using the diffractometers D2 and D4 at ILL. A first-order difference method has been used to determine the change in the intermolecular contributions to the observed cross-section. Fourier transformation techniques are used to give the changes in the real space distribution function. The results confirm the preliminary observations obtained in an earlier experiment and give a more precise indication of the structural variation. A detailed analysis shows that the intermolecular OD separation which corresponds to an effective hydrogen bond distance increases as the temperature rises. At larger distances there is a systematic but more complex variation which may be attributed to a change in the relative orientations of neighbouring molecules.