When water is cooled below its normal freezing point, it normally freezes to form hexagonal ice, or Ice I. If it is very pure and cooled carefully, it may be supercooled to about −42 °C. If water is cooled very rapidly then it forms an amorphoric glass.
LDA, Low-density amorphous ice, may be prepared from hyperquenched glassy water, as above, or by warming high density amorphous ice (HDA) to just above 120 K at normal atmospheric pressure. LDA shows behavior more similar to a crystalline material rather than the amorphous glass it is. LDA is expected to be an extension of supercooled liquid water.
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