Absence of amorphous forms when ice is compressed at low temperature
Chris A Tulk1, Jamie J Molaison2, Adam R Makhluf3
1Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN, USA. tulkca@ornl.gov.
Nature
|May 24, 2019
Summary
Compression kinetics influence amorphous ice formation. Slow compression of ice I at 100 K yields crystalline phases, not high-density amorphous ice (HDA), challenging the two-liquid water model for amorphous ice.
Area of Science:
- Materials Science
- Physical Chemistry
- Condensed Matter Physics
Background:
- Amorphous water ice exists in multiple forms lacking crystalline order.
- High-density amorphous ice (HDA) was previously thought to be a glassy state, influencing the two-liquid water model for supercooled water anomalies.
- Alternative theories suggested HDA forms due to mechanical instability and sluggish kinetics.
Purpose of the Study:
- To investigate the role of kinetics in the formation of amorphous ice phases.
- To challenge existing theories linking amorphous ice to supercooled liquid water.
- To explore the compression pathways of ice I under varying kinetic conditions.
Main Methods:
- Compression of ice I at 100 Kelvin under controlled, slow kinetic conditions.
- Comparison of outcomes from slow versus fast compression protocols.
- Structural analysis of resulting ice phases, including proton ordering and interpenetration.
Main Results:
- Slow compression of ice I at 100 K produced crystalline phases: ice IX', ice XV', and ice VIII'.
- Fast compression at 100 K yielded high-density amorphous ice (HDA) but not ice IX'.
- Direct transformation of ice I to ice XV' was found to be structurally inhibited.
Conclusions:
- Amorphous ice formation is a kinetically arrested transformation between low-density ice I and high-density ice XV'.
- The study challenges the connection between amorphous ice phases and the two-liquid model of supercooled water.
- Kinetics, not thermodynamic melting, are crucial in determining the formation of amorphous versus crystalline ice structures.
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