Visual Observations of the Amorphous-Amorphous Transition in H 2 O Under Pressure

Abstract
The vapor-deposited low-density amorphous phase of H2O was directly compressed at 77 kelvin with a diamond-anvil cell, and the boundary between the low-density amorphous phase and the high-density amorphous phase was observed while the sample was warmed under compression. The transition from the low-density amorphous phase to the high-density amorphous phase was distinct and reversible in an apparently narrow pressure range at ∼130 to ∼150 kelvin, which provided experimental evidence for polymorphism in amorphous H2O.