I'm curious about about an upper limit of temperature at which water can no longer exist in a solid state even as pressure increases. There are "ice" phase states such as VII and X which are apparently solid up to 600K under pressures over 10^9 Pa. Phase X is called a "proton ordered" state. Is there some theoretical temperature where the solid state can no longer be maintained despite increasing pressure short of that of a plasma? http://en.wikipedia.org/wiki/Ice See sec 7 phase state chart.