Superionic water is a theoretical phase of water under extreme heat and pressure which has properties of both a solid and a liquid.
Contents
At high temperatures and pressures, such as in the interior of giant planets, it is argued that water exists as ionic water in which the molecules break down into a soup of hydrogen and oxygen ions. At even higher pressures, ionic water will further condense into superionic water, where the oxygen crystallises and the hydrogen ions float around freely within the oxygen lattice.
Properties
Superionic water is thus far theoretical, but predictions have been made about its properties. If it were present on Earth, it would rapidly decompress and explode. Under the conditions theorized to cause water to enter the phase, it is believed that superionic water would be as hard as iron and would glow yellow.
As of 2013 it is theorized that superionic ice can possess two crystalline structures. At pressures in excess of 0.5 Mbar it is predicted that superionic ice would take on a body-centered cubic structure. However, at pressures in excess of 1 Mbar it is predicted that the structure would shift to a more stable face-centered cubic lattice.
History of theoretical and experimental evidence
In 1999 Cavazzoni, et al. predicted that such a state would exist for ammonia and water in conditions such as those existing on Uranus and Neptune. In 2005 Laurence Fried led a team at Lawrence Livermore National Laboratory in California to recreate the formative conditions of superionic water. Using a technique involving smashing water molecules between diamonds and super heating it with lasers they observed frequency shifts which indicated that a phase transition had taken place. The team also created computer models which indicated that they had indeed created superionic water. In 2013 Hugh F. Wilson, Michael L. Wong, and Burkhard Militzer at the University of California, Berkeley published a paper predicting the face-centered cubic lattice structure that would emerge at higher pressures.
Existence in ice giants
It is theorized that the ice giant planets Uranus and Neptune hold a layer of superionic water.