Polyamorphic transformations in liquids and glasses

Crystalline solids undergo large changes in their structure and properties as they transform between different polymorphs in response to the pressure and the temperature. It now appears that analogous density- or entropy-driven phase transitions also occur within the liquid state: these represent a new type of general phenomena that occur within liquids, that is only just beginning to be recognised and understood. Such polyamorphic transformations are also reflected within the solid amorphous state, as rapid and often dramatic changes in the structure and properties of glasses and amorphous solids that occur during compression, or as a function of the quench conditions.