Structural mechanism leading to a ferroelastic glass state: Interpretation of amorphization under pressure

The concept of a ferroelastic glass, the mechanical analog of dipole and spin glasses, is introduced. The structural mechanism leading to a ferroelastic glass state, which is formed by a distribution of randomly oriented nanoscale ferroelastic domains, is described and justified theoretically. It is shown to provide a consistent interpretation of the amorphization under pressure of a number of materials, such as Cs₂HgBr₄, α-quartz, and ice, and a coherent link between previous models of pressure-induced amorphization. It also clarifies the microstructural properties disclosed in some ferroelectric relaxors.