The Structure of Liquid Water by Neutron Scattering. II. Temperature Dependence of the Liquid Structure

The structure factors for heavy water at 25, 50, 70, and 95 °C were determined in the range of Q, 1.4–20 Å−1, by means of the time-of-flight (TOF) neutron diffraction method using the electron linear accelerator (LINAC). An analysis of the neutron diffraction data was made by applying a new general theoretical procedure of analysis for the fluid system composed of molecular clusters with various sizes. Structure factors were calculated according to the general procedure for the pentamer-monomer mixture model as a mixture of regular tetrahedral pentamers and non-bonded monomers with a due assignment of pentamer fraction at each temperature. Excellent agreement was obtained between the calculated and observed structure factors at temperatures in 25–95 °C. Combined with the preceding result (N. Ohtomo, K. Tokiwano, and K. Arakawa, Bull. Chem. Soc. Jpn., 54, 1802 (1981)), it was concluded that the pentamer-monomer mixture model is the best one for water from room temperature to near the boiling point.