New high-pressure transformation in α-quartz

Abstract

Recent experimental and theoretical studies report that quenched pressure-amorphized \ensuremath{\alpha}-quartz is elastically anisotropic and displays a reversal of anisotropy with respect to the original crystallographic orientation. We demonstrate that samples recovered from static compression experiments of \ensuremath{\alpha}-quartz exhibit an unusual pressure-induced microstructure, which arises from a new phase transformation in \ensuremath{\alpha}-quartz at 21 GPa. Upon decompression, the high-pressure phase reverts to a quartzlike structure in a twinned state, accounting for the previously reported elastic behavior.