Inelastic neutron scattering study of water in the subcritical and supercritical region

Inelastic neutron scattering measurements have been carried out at high-energy transfers on H₂O water in the subcritical and supercritical region. The results were compared to estimated values of the kinetic energy of a hydrogen atom in a water molecule in the gas and liquid states. It was found that the increase in kinetic energy with temperature was more than expected from the harmonic approximation. It is concluded that about half the hydrogen bonds in water with density of p=0.85 g/cm³ are broken at 400 °C. It was also found that there was a further decrease in the number of hydrogen bonds on decreasing the density at 400 °C.