Melting and pressure-induced amorphization of quartz

It has recently been shown that amorphization and melting of ice (O. MISHIMA, Nature, 384 (1996) 546) were intimately linked. In this letter, we infer from molecular-dynamics simulations on the SiO2 system that the extension of the alpha-quartz melting line in the metastable pressure-temperature domain is the pressure-induced amorphization line. It seems therefore likely that melting is the physical phenomenon responsible for pressure-induced amorphization. Moreover, we show that the structure of a "pressure glass" is similar to that of a very rapidly (10(13) to 10(14) kelvins per second) quenched thermal glass.