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A Microfluidic Approach for the Study of Ice and Clathrate Hydrate Crystallization
Published on: August 18, 2022
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Fluctuations and local ice structure in model supercooled water
1Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
The Journal of Chemical Physics
|September 7, 2015
Summary
Simulations show that apparent liquid-liquid phase separation in water models is due to long-range correlations between ice-like molecules, not true phase separation. These correlations are system-size dependent and do not occur in large simulations.
Area of Science:
- Physical Chemistry
- Computational Chemistry
- Materials Science
Background:
- Investigating water models near proposed liquid-liquid critical points is crucial for understanding water's anomalous behavior.
- Previous simulations suggested liquid-liquid phase separation in TIP4P/2005 and TIP5P water models under supercooled conditions.
Purpose of the Study:
- To analyze local structures and fluctuations in TIP4P/2005 and TIP5P water models under deeply supercooled conditions.
- To determine if observed liquid-liquid phase separation is a genuine phenomenon or an artifact of simulation conditions.
Main Methods:
- Large-scale molecular dynamics simulations (up to 32,000 molecules) were performed for TIP4P/2005 and TIP5P water models.
- Analysis focused on local molecular structures, fluctuations, and correlations under deeply supercooled conditions.
- System size dependence was systematically investigated.
Main Results:
- Strong, long-range (∼4 nm) correlations between molecules with local ice-like structures were observed.
- These ice-like correlations were found to be strongly correlated with tetrahedral liquid structures and density fluctuations.
- Apparent liquid-liquid phase separation showed significant system size dependence and disappeared in the largest simulations.
Conclusions:
- The observed density differences in smaller simulations are attributed to long-range correlations between ice-like molecules.
- The results suggest that the TIP4P/2005 and TIP5P water models do not exhibit spontaneous liquid-liquid phase separation under the simulated conditions.
- The findings challenge previous interpretations of liquid-liquid phase separation in these water models based on smaller simulation cells.
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