Amorphous ice

Amorphous ice (non-crystalline or "vitreous" ice) is an amorphous solid form of water. Common ice is a crystalline material wherein the molecules are regularly arranged in a hexagonal lattice, whereas amorphous ice lacks long-range order in its molecular arrangement. Amorphous ice is produced either by rapid cooling of liquid water (so the molecules do not have enough time to form a crystal lattice), or by compressing ordinary ice at low temperatures.

Although almost all water ice on Earth is the familiar crystalline ice I_h, amorphous ice dominates in the depths of interstellar medium, making this likely the most common structure for H₂O in the universe at large.

Just as there are many different crystalline forms of ice (currently more than seventeen are known), there are also different forms of amorphous ice, distinguished principally by their densities.

Amorphous ices have the property of suppressing long-range density fluctuations and are, therefore, nearly hyperuniform. Despite the epithet "amorphous", analysis utilizing neural network classification has shown that amorphous ices are glasses.