title: Changes in the structure of water deduced from the pressure dependence of the Raman OH frequency.
abstract: We report on the Raman spectra of water under high temperature and pressure conditions and show a discontinuity in the pressure dependence of the OH stretching frequency. As pressure increases, the strength of hydrogen bonding increases rapidly in the pressure ranges up to 0.4+/-0.1 GPa at 25 degrees C, 1.0+/-0.1 GPa at 100 degrees C, and 1.3+/-0.1 GPa at 300 degrees C and slowly above these pressures. This finding clearly demonstrates the existence of discontinuities in the pressure response of the hydrogen bonds of water, which suggests a possible structural change under these conditions.
authors.affiliation: Institute for Geothermal Sciences, Graduate School of Science, Kyoto University, Beppu 874-0903, Japan. kawamoto@bep.vgs.kyoto-u.ac.jp
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Kawamoto
authors.forename: Shukichi
authors.initials: S
authors.lastname: Ochiai
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kagi