Scientists Create Hexagonal Packed Ice at Extreme Pressures

Researchers led by Alexis Forestier synthesized a new phase of water ice with a hexagonal close-packed (HCP) oxygen sublattice at pressures above 200 GPa and temperatures near 2000 K. Published in Physical Review Letters, the work offers clues about the interiors of ice giants like Neptune and Uranus.

• HCP phase formed above 200 GPa and around 2000 K
• Experiment used a diamond anvil with laser heating and synchrotron X-ray diffraction
• A mixed FCC-HCP phase appeared at intermediate pressures
• Above 80 GPa water previously forms ice X with a body-centered cubic lattice