Stability of hydrogen-filled hexagonal ice under high pressure
1Department of Chemistry, Zhejiang University, Hangzhou 310028, People's Republic of China.
The Journal of Chemical Physics
|December 15, 2025
Summary
Researchers explored hydrogen-filled ice Ih (CIh hydrate), finding it stable at gigapascal pressures. This discovery offers insights into giant planet composition and potential hydrogen energy storage solutions.
Area of Science:
- Materials Science
- Planetary Science
- Physical Chemistry
Background:
- Hydrogen hydrates (H2O + H2) are crucial for understanding giant planets and energy storage.
- H2-filled ice Ic (C2 hydrate) is stable above 2 GPa, but H2-filled ice Ih (CIh hydrate) remains understudied.
Purpose of the Study:
- To investigate the possibility and stability of H2-filled ice Ih (CIh hydrate).
- To determine the conditions under which CIh hydrate forms and its thermodynamic stability.
Main Methods:
- Hybrid grand-canonical Monte Carlo and isothermal-isobaric molecular dynamics simulations.
- Free energy calculations to assess thermodynamic stability.
Main Results:
- Ice Ih can absorb H2 up to an H2-to-H2O ratio of 0.5 under compression.
- CIh hydrate is thermodynamically stable at a few gigapascals.
- CIh hydrate occupies stability conditions previously assigned to C1 hydrate.
Conclusions:
- The study confirms the existence and stability of CIh hydrate.
- Findings advance understanding of H2O-H2 systems under pressure.
- This has implications for planetary science and hydrogen storage technologies.
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