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.

Lithium speciation in aqueous fluids at high P and T studied by ab initio molecular dynamics and consequences for Li-isotope fractionation between minerals and fluids

“…Together with the steeper slope of the O-O distance this indicates a change in compaction mechanism from structural rearrangements to bond shortening. Structural changes around a density of 1.2 g/cm 3 have also been reported for liquid water at high temperature (up to 573 K) (Kawamoto et al, 2004). Regarding Li speciation, we observe appreciable Li in 6-fold coordination only at densities above 1.2 g/cm 3 .…”

Probing the hydrogen-bond network of water via time-resolved soft X-ray spectroscopy

“…Similar insensitivity of the main edge is also observed in the XRS difference spectrum of H 2 O and D 2 O where the changes in the pre-edge and post-edge follow an expected small difference in temperature. Opposing effects of pressure and temperature on hydrogen bonding have been inferred from pressure-dependent Raman spectroscopy on the OH stretching vibration of water 66 but the interplay between temperature and pressure with respect to the oxygen K-edge is not clear and modelling of this edge at elevated pressure is necessary to extract more information from transient x-ray absorption spectra.…”

Laser-driven shock experiments on precompressed water: Implications for “icy” giant planets

“…Successful DAC experiments have been carried out on water to 210 GPa at temperatures near 300 K ͑Refs. 11 and 12͒ and at lower pressures but higher temperatures, [13][14][15][16][17][18][19] leaving much of the pressure range relevant to the icy layer uninvestigated ͑Fig. 1͒.…”