# What is the meaning of “superionic”?

I see the term "superionic" applied to high pressure water in articles like Giant planets may host superionic water, but I don't understand what the term really means.

How is "superionic" distinguished from simply "ionic"?

Why does the article refer to hydrogen "atoms", which would imply that they are neutral, as opposed to protons or hydronium or some other actual ion?

• Written by an intern? You will probably have to read the original articles by Laurence E. Fried: Phys. Rev. Lett. 2005, 94, 217801 and Phys. Rev. Lett. 2005, 94, 125508 – Klaus-Dieter Warzecha Mar 3 '15 at 15:31
• @KlausWarzecha Those articles helped some. Seems that there are H2O, H3O+ and OH- species that are all very shortlived and protons are moving much more than the oxygens. But still I don't comprehend any defining characterists that would let me know when to use the term "superionic". For superconductor or superfluid there is a clear defining property, but I don't seen anything like that for superionic. – DavePhD Mar 3 '15 at 16:19
• en.wikipedia.org/wiki/Superionic_water – Mithoron Mar 3 '15 at 17:02
• @Mithoron I still don't understand – DavePhD Mar 3 '15 at 17:11
• nature.com/nmat/journal/v10/n9/full/nmat3066.html - it seems superionic means possesing extremely high ionic conductivity – Mithoron Mar 3 '15 at 17:19

It is where the water only exists as a mixture of $\ce{H+}$ and $\ce{OH-}$ ions. At high pressures, the oxygen crystallises, leaving the hydrogen ions free - thus making superionic water highly conductive.