Structural response of alpha-quartz under plate-impact shock compression

Due to its far-reaching applications in geophysics and materials science, quartz has been one of the most extensively examined materials under dynamic compression. Despite 50 years of active research, questions remain concerning the structure and transformation of SiO2 under shock compression. Continuum gas-gun studies have established that under shock loading quartz transforms through an assumed mixed-phase region to a dense high-pressure phase. While it has been often assumed that this high-pressure phase corresponds to the stishovite structure observed in static experiments, there has been no atomic-level structure data confirming this. In this study, we use gas-gun shock compression coupled with in-situ synchrotron X-ray diffraction to interrogate the crystal structure in shock-compressed alpha-quartz up to 65 GPa. Our results reveal that alpha-quartz undergoes a phase transformation to a disordered metastable phase as opposed to crystalline stishovite or an amorphous phase, challenging long-standing assumptions about the dynamic response of this fundamental material.