Viscosity and Stokes-Einstein relation in deeply supercooled water under pressure
Alexandre Mussa1, Romain Berthelard1, Frédéric Caupin1
1Institut Lumière Matière, Université de Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Universitaire de France, F-69622 Villeurbanne, France.
The Journal of Chemical Physics
|October 17, 2023
Summary
Researchers measured water viscosity under high pressure and low temperature, revealing non-Arrhenius behavior and a pressure-induced viscosity decrease. This suggests a potential liquid-liquid critical point in water.
Area of Science:
- Physical chemistry
- Thermodynamics
- Fluid dynamics
Background:
- Water exhibits complex behavior under extreme conditions.
- Understanding water's properties is crucial for various scientific disciplines.
Purpose of the Study:
- To measure shear viscosity (η) in water at high pressures (up to 150 MPa) and low temperatures (down to 229.5 K).
- To investigate the temperature and pressure dependence of water's viscosity.
- To examine the validity of the Stokes-Einstein relation in supercooled water.
Main Methods:
- Experimental measurement of shear viscosity (η) in water.
- Data analysis of temperature and pressure dependencies.
- Comparison with literature data for self-diffusion coefficient (Ds).
Main Results:
- Non-Arrhenius temperature dependence of viscosity observed at all pressures.
- Qualitatively different temperature dependence at 0.1 MPa compared to pressures above 20 MPa.
- Non-monotonic pressure dependence with a >50% viscosity decrease at low temperatures.
- Observed temperature and pressure dependence of Dsη/T analogous to simulations of a realistic water model.
Conclusions:
- Water's viscosity exhibits complex behavior under high pressure and low temperature.
- The Stokes-Einstein relation's behavior in supercooled water aligns with simulations.
- Findings suggest compatibility with a liquid-liquid critical point in water at positive pressure.
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