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Updated: Jun 30, 2026
07:48
An Externally-Heated Diamond Anvil Cell for Synthesis and Single-Crystal Elasticity Determination of Ice-VII at High Pressure-Temperature Conditions
Published on: June 18, 2020
Melting of ice under pressure
Eric Schwegler1, Manu Sharma, François Gygi
1Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA. schwegler@llnl.gov
Summary
Investigating ice-VII melting under pressure reveals it behaves as a molecular solid up to 40 GPa. Above 45 GPa, molecular dissociation and proton diffusion alter the melting curve significantly.
Area of Science:
- Geophysics
- Materials Science
- Computational Chemistry
Background:
- High-pressure phases of water ice are crucial for understanding planetary interiors.
- Ice-VII is a high-pressure polymorph relevant to icy moons and Earth's deep mantle.
- Previous experimental data on ice-VII melting points exist but require theoretical validation.
Purpose of the Study:
- To computationally determine the melting temperature of ice-VII across a range of high pressures.
- To elucidate the microscopic mechanisms governing ice-VII melting.
- To investigate the role of molecular dissociation and proton diffusion in the melting process.
Main Methods:
- First-principles molecular dynamics simulations were employed.
- A two-phase approach was utilized to calculate melting temperatures.
- Simulations covered pressures from 10 to 50 GPa.
Main Results:
- Computed melting temperatures align with experimental diamond anvil cell data.
- Ice-VII melts as a molecular solid between 10 and 40 GPa.
- Above ~45 GPa, a steeper melting curve is observed due to molecular dissociation and proton diffusion.
Conclusions:
- The study provides a theoretical framework for understanding ice-VII melting behavior.
- Proton diffusion in ice-VII shows gradual onset, resembling superionic solids.
- Computational findings support experimental observations of high-pressure ice phases.
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