A New Phase of Superionic Ice
canopic jug writes:
ScienceAlert has a summary of a report on a new phase of superionic ice as developed in the lab.
Scientists confirmed in 2019 what physicists had predicted back in 1988: a structure where the oxygen atoms in superionic ice are locked in a solid cubic lattice, while the ionized hydrogen atoms are let loose, flowing through that lattice like electrons through metals.
This gives superionic ice its conductive properties. It also raises its melting point such that the frozen water remains solid at blistering temperatures.
In this latest study, physicist Arianna Gleason of Stanford University and colleagues bombarded thin slivers of water, sandwiched between two diamond layers, with some ridiculously powerful lasers.
Successive shockwaves raised the pressure to 200 GPa (2 million atmospheres) and temperatures up to about 5,000 K (8,500 F) - hotter than the temperatures of the 2019 experiments, but at lower pressures.
"Recent discoveries of water-rich Neptune-like exoplanets require a more detailed understanding of the phase diagram of [water] at pressure-temperature conditions relevant to their planetary interiors," Gleason and colleagues explain in their paper, from January 2022.
X-ray diffraction then revealed the hot, dense ice's crystal structure, despite the pressure and temperature conditions only being maintained for a fraction of a second.
The resulting diffraction patterns confirmed the ice crystals were in fact a new phase distinct from superionic ice observed in 2019. The newly discovered superionic ice, Ice XIX, has a body-centered cubic structure and increased conductivity compared to its predecessor from 2019, Ice XVIII.
Superionic ice might be the most common form of water in the universe.
Cite: Dynamic compression of water to conditions in ice giant interiors
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