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Published on: May 26, 2021
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Transitions in pressure collapsed clathrate hydrates.
Ove Andersson1, Yasuhiro Nakazawa
1Department of Physics, Umeå University , 901 87 Umeå, Sweden.
The Journal of Physical Chemistry. B
|February 18, 2015
Summary
Type II clathrate hydrates (CHs) share ice-like structural transitions. Collapsed CHs exhibit similar amorphous ice transitions, offering insights into water
Area of Science:
- Materials Science
- Physical Chemistry
- Thermodynamics
Background:
- Type II clathrate hydrates (CHs) are inclusion compounds with water cages encapsulating guest molecules.
- Both CHs and ice can collapse to amorphous states under pressure below 140 K.
- These collapsed states exhibit a glass transition at 140 K and 1 GPa, mirroring high-density amorphous ice.
Purpose of the Study:
- To investigate the transition behavior of collapsed type II clathrate hydrates.
- To compare the transition properties of collapsed CHs with those of pure water.
- To explore the implications for models of water's anomalous properties.
Main Methods:
- Utilized thermal conductivity measurements.
- Employed dielectric measurements.
- Studied type II CHs with tetrahydrofuran and 1,3 dioxolane guest molecules.
Main Results:
- Collapsed CHs, after heating above their glass transition, show transitions analogous to the high-to-low density amorphous ice transition.
- These transitions occur at slightly shifted temperature-pressure coordinates compared to pure water.
- Collapsed CHs are more stable than collapsed ice, allowing study over a broader T-p range.
Conclusions:
- Collapsed clathrate hydrates display transition behaviors consistent with cold water.
- This supports models explaining water's properties via two distinct liquid states.
- Observed sluggish homogenizing and phase separation processes influence CH transition behaviors.
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