Ice subjected to unimaginable pressure could eventually conduct electricity like a metal.
The ice we encounter every day has a well-known structure: water molecules assemble into a solid network. But when pressure increases enormously, atoms can change their arrangement. Researchers already know of many forms of ice, very different from the ice in our freezers.
Illustration: Pixabay
A team used calculations to explore what could happen at even higher pressures. The researchers therefore used simulations describing the behavior of atoms and electrons to search for structures capable of remaining stable.
The calculations first predict a new arrangement at around 300 GPa, or nearly 3 million times atmospheric pressure. A second structure would then become stable at around 2,120 GPa. In this latter structure, oxygen atoms form an especially compact cubic arrangement.
The most astonishing transformation would occur beyond approximately 2,600 GPa. At this pressure, the calculations indicate that the energy gap normally preventing electrons from moving freely disappears. The ice would then adopt metallic behavior and could conduct electricity.
Everything happens on the oxygen atom side. Under such intense compression, they become extremely close together. Their electrons can then interact, and this proximity would eliminate the nearly insulating nature of the ice we know.
These pressures far exceed those accessible in ordinary environments. They may nevertheless be relevant for understanding matter buried deep inside certain giant planets.
The predicted phase still needs to be confirmed experimentally. Producing and directly observing this ice at more than 2,600 GPa would, however, require experimental conditions that are particularly difficult to achieve.