Metallic Water

Metallic Water, an electrically conducting form of water, might exist under just the right conditions of temperature and pressures on gas giant planets like Jupiter or ice giants like Neptune. Ice on Earth comes in many forms---the normal hexagonal ice (manifested as crystalline ice or as six-sided snowflakes), cubic ice (which is rare; it can form as tiny crystallites high in the atmosphere), and other types which vary according to pressure conditions.

A new theoretical study by physicists at Sandia National Lab shows that a conducting phase of water could occur at a temperature of 4000 K and a pressure of 100 gigapascals, which are much more forgiving than the previous estimates---7000 K and 250 GPa, respectively---and thought to exist inside Jupiter and Neptune (for a drawing of this metallic water, see www.aip.org/png ).

Furthermore, the new work shows, unexpectedly, that on a pressure-vs-temperature phase diagram the conducting phase of water ice should sit right next to electrically insulating ice, also called “superionic” ice, since in that case a water molecule’s two hydrogen atoms are free to move about while the oxygen atoms remain frozen in place.

According to Thomas Mattsson (trmatts@sandia.gov, 505-844-9215), one of the Sandia researchers, one aim of his study of high energy density water (with densities more than twice the usual 1 g/cm^3 density) is to better understand the short-lived high-temperature, high-pressure fluid environment inside Sandia’s Z Machine, the device where huge a huge portion of electrical charge (stored in capacitor banks immersed in oil) is sent all at once through wires, producing a huge batch of soft x rays (see http://www.aip.org/pnu/2004/split/702-1.html). (Mattsson and Desjarlais, Physical Review Letters, 7 July 2006)