Amorphous ice is a solid phase of water that lacks crystal structure. It is stable below about 150K, above which it converts to crystalline ice.

There are four phases of amorphous ice: low medium, high, and very high density. Medium density is a very recent discovery and can be created by grinding ice at 77K.

Do these phases exist on a spectrum? There is no "in between" for different crystalline phases. But amorphous states do not have a precisely defined structure. If so there would be an amorphous ice with any density between 0.95 and 1.25 g/cm^3.

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    $\begingroup$ Given the different ice phases, it is conceivable that there could be amorphous ices with different radial distribution functions and a first order transition to a different radial distribution function. $\endgroup$
    – Jon Custer
    Commented Apr 10, 2023 at 1:03

1 Answer 1


According to Wikipedia, yes

Polyamorphism occurs when there is a first order phase transition between two glass phases. Water ice is one of the examples.

Glass phases are never thermodynamicly stable, the substance at the given T and P would rather be in a crystalline (or in very rare cases quaiscrystalline) phase.

A glass-glass phase transition only occurs when the molecules are kinetically free enough rearrange a bit but not free enough to find the crystal phase. In ice, which really wants to crystalize it's a minor miracle that such a transition can be observed.


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