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Title: Gradual crossover in molecular organization of stable liquid H{sub 2}O at moderately high pressure and temperature

Using the literature raw data of the speed of sound and the specific volume, the isothermal compressibility, κ{sub T}, a second derivative thermodynamic quantity of G, was evaluated for liquid H{sub 2}O in the pressure range up to 350 MPa and the temperature to 50 ºC. We then obtained its pressure derivative, dκ{sub T}/dp, a third derivative numerically without using a fitting function to the κ{sub T} data. On taking yet another p-derivative at a fixed T graphically without resorting to any fitting function, the resulting d{sup 2}κ{sub T}/dp{sup 2}, a fourth derivative, showed a weak but clear step anomaly, with the onset of the step named point X and its end point Y. In analogy with another third and fourth derivative pair in binary aqueous solutions of glycerol, dα{sub p}/dx{sub Gly} and d{sup 2}α{sub p}/dx{sub Gly}{sup 2}, at 0.1 MPa (α{sub p} is the thermal expansivity and x{sub Gly} the mole fraction of solute glycerol) in our recent publication [J. Solution Chem. 43, 663-674 (2014); DOI:10.1007/s10953-013-0122-7], we argue that there is a gradual crossover in the molecular organization of pure H{sub 2}O from a low to a high p-regions starting at point X and ending at Y at amore » fixed T. The crossover takes place gradually spanning for about 100 MPa at a fixed temperature. The extrapolated temperature to zero p seems to be about 70 – 80 °C for points X and 90 – 110 °C for Y. Furthermore, the mid-points of X and Y seem to extrapolate to the triple point of liquid, ice Ih and ice III. Recalling that the zero x{sub Gly} extrapolation of point X and Y for binary aqueous glycerol at 0.1 MPa gives about the same T values respectively, we suggest that at zero pressure the region below about 70 °C the hydrogen bond network is bond-percolated, while above about 90 ºC there is no hydrogen bond network. Implication of these findings is discussed.« less
 [1] ;  [2] ; ; ;  [3]
  1. Department of Chemistry, The University of British, Columbia, Vancouver, BC, Canada V6T 1Z1, and Suitekijuku, Vancouver, BC, Canada V6R 2P5 (Canada)
  2. NSM, Research Unit for Functional Biomaterials, Roskilde University, Roskilde, Denmark DK-4000 (Denmark)
  3. Research Center for Structural Thermodynamics, Osaka University, Toyonaka, Osaka, Japan 560-0043 (Japan)
Publication Date:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Advances; Journal Volume: 4; Journal Issue: 9; Other Information: (c) 2014 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States