Pressure-induced amorphization versus decomposition

Pressure-induced amorphization of crystalline compounds is believed to arise due to kinetic hindrance of equilibrium phase transitions, while the final state remains speculative/unknown in most instances. Here, we examine an alternate route to amorphization that it could arise in many complex systems if equilibrium decomposition to more dense-packed daughter compounds is constrained kinetically. It is shown that many systems that exhibit pressure-induced amorphization are also good candidates for pressure-induced decomposition leading to a disordered assemblage, forming equilibrium crystalline materials when subjected to elevated temperatures. The route explains the results in Fe2SiO4 and CaAl2Si2O8 and predicts decomposition of several other compounds at high pressure.