Superionic water

Superionic water is a phase of water under extreme heat and pressure which has properties of both a solid and a liquid, which is supported by some experimental evidence.[1][2][3][4]

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.[5]

Properties

Superionic water was previously theoretical, but predictions were 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.[4]

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.[6]

History of theoretical and experimental evidence

Demontis, et al. made the first prediction for superionic water using classical molecular dynamics simulations that were published in Physical Review Letters in 1988 [7]. 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.[8]. 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.[4] 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.[6]

Additional experimental evidence was found by Marius Millot and colleagues in 2018, in an article in Nature Physics, by inducing high pressure on water between diamonds and then shocking the water using a laser pulse.[2].

February 2018 experiment

The most recent experiment was conducted at Lawrence Livermore by squeezing water between two pieces of diamond with a pressure of 360,000 psi. The water was squeezed into type VII ice which is 60 percent denser than normal water.[9]

The compressed ice was then transported to the University of Rochester where it was blasted by a pulse of laser light. The reaction created conditions like those inside of ice giants such as Uranus and Neptune by heating up the ice thousands of degrees under a pressure a million times greater than the earth's atmosphere in only ten to 20 billionths of a second.

The experiment concluded that the current in the conductive water was indeed carried by ions rather than electrons and thus pointed to the water being superionic.[9]

Existence in ice giants

It is theorized that the ice giant planets Uranus and Neptune hold a layer of superionic water.[10] But there are also studies that suggest that other elements present inside the interiors of these planets, particularly carbon, may prevent the formation of superionic water.[11]

References

  1. ↑ Dynamic Ionization of Water under Extreme Conditions, Alexander F. Goncharov, Nir Goldman, Laurence E. Fried, Jonathan C. Crowhurst, I-Feng W. Kuo, Christopher J. Mundy, and Joseph M. Zaug, Phys. Rev. Lett. 94, 125508, 2005
  2. 1 2 Millot, Marius; et al. (5 February 2018). "Experimental evidence for superionic water ice using shock compression". Nature Physics. Bibcode:2018NatPh..14..297M. doi:10.1038/s41567-017-0017-4. Retrieved 5 February 2018.
  3. ↑ Chang, Kenneth (5 February 2018). "Newly Discovered Form of Water Ice Is 'Really Strange' - Long theorized to be found in the mantles of Uranus and Neptune, the confirmation of the existence of superionic ice could lead to the development of new materials". The New York Times. Retrieved 5 February 2018.
  4. 1 2 3 Giant planets may host superionic water, Nature, 22 March 2005.
  5. ↑ Weird water lurking inside giant planets, New Scientist,01 September 2010, Magazine issue 2776.
  6. 1 2 Phys.org, "New phase of water could dominate the interiors of Uranus and Neptune", Lisa Zyga, 25 April 2013
  7. ↑ New high-pressure phases of ice, P. Demontis, R. LeSar, and M. L. Klein, Phys. Rev. Lett., vol. 60, no. 22, pp. 2284–2287, May 1988
  8. ↑ Superionic and Metallic States of Water and Ammonia at Giant Planet Conditions, Cavazzoni C., et al. Science, 283. 44 - 46
  9. 1 2 Chang, Kenneth (2018-02-05). "New Form of Water, Both Liquid and Solid, Is 'Really Strange'". The New York Times. ISSN 0362-4331. Retrieved 2018-02-13.
  10. ↑ Charlie Osolin. "Public Affairs Office: Recreating the Bizarre State of Water Found on Giant Planets". Llnl.gov. Retrieved 24 December 2010.
  11. ↑ Chemical processes in the deep interior of Uranus, Ricky Chau, Sebastien Hamel & William J. Nellis, Nat. Commun., https://dx.doi.org/10.1038/ncomms1198, 2011.
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