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Liquid-liquid critical point in heavy water
1National Institute for Research in Inorganic Materials (NIRIM), 1-1 Namiki, Tsukuba, 305-0044, Japan and Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Corporation (JST), Kawaguchi, Saitama, 332-001.
Physical Review Letters
|September 16, 2000
Summary
The study measured melting curves for heavy water (D2O) ices. Findings support the liquid-liquid critical-point hypothesis, suggesting two distinct liquid states of water merge at a critical point.
Area of Science:
- Physical Chemistry
- Materials Science
- Thermodynamics
Background:
- The liquid-liquid critical-point hypothesis proposes two distinct liquid states of water at low temperatures.
- These states are theorized to merge at a critical point, influencing water's phase behavior.
Purpose of the Study:
- To investigate the low-temperature metastable melting curves of heavy water (D2O) ices.
- To determine if experimental data supports the existence of a liquid-liquid critical point in D2O.
Main Methods:
- Experimental measurement of low-temperature metastable melting curves for D2O ice III and D2O ice IV.
- Analysis of the slope changes in the melting curves under varying pressure and temperature conditions.
Main Results:
- The melting curve of D2O ice III exhibited a smooth curvature around 25 MPa and 238 K.
- The melting curve of D2O ice IV showed an abrupt change in slope at 100 MPa and 220 K.
Conclusions:
- The observed melting curve anomalies in D2O ices are consistent with the presence of a liquid-liquid critical point.
- This finding provides experimental evidence supporting the liquid-liquid critical-point hypothesis for water.