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. (C) 2000 Elsevier Science Ltd. All rights reserved.