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

Abstract

Because of 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 often been assumed that this high-pressure phase corresponds to the stishovite structure observed in static experiments, there have been no crystal 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 of shock-compressed α-quartz up to 65 GPa. Our results reveal that α-quartz undergoes a phase transformation to a disordered metastable phase as opposed to crystalline stishovite or an amorphous structure, challenging long-standing assumptions about the dynamic response of this fundamental material.

Evidence for a rosiaite-structured high-pressure silica phase and its relation to lamellar amorphization in quartz

“…Our quartz samples are compressed at room temperatures, while the temperatures of shock-compressed quartz in the mixed phase region are commonly on the order of 300–500 °C 10 , 12 , 40 . The shock gas gun data match well the Hugoniot curve at high pressures between 40 and 65 GPa, where the shock temperatures are also significantly enhanced and the phase transformation should be completed 19 . Without further experiments exploiting comprehensively the influences of pressures, temperatures, and strain rates on the phase transformations, it seems difficult to conclusively interpret the Hugoniot curve from the onset of the mixed phase region to the very high-pressure regime.…”

“…This most general description of the structure of high-pressure polymorphs possesses the space group symmetry and dimensions of a perfect hcp lattice (P6 3 /mmc) with a = 2.563 Å and c = 4.112 Å 31 , 32 . This phase was reported to occur in diamond anvil cells as well as shock experiments 18 , 19 , 31 , 32 and it was recently suggested to be the phase that forms in the mixed phase regime of the Hugoniot curve 19 . The defective niccolite phase is historically labeled to be Fe 2 N structured 31 , 32 .…”

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Fig. 6 Pressure-density diagram displaying Hugoniot 12 , 42 , 43 and X-ray diffraction data 19 derived from shock experiments on quartz in comparison to density data of hydrostatic diamond anvil cell (DAC) experiments 55 , 56 and to our rapid compressed samples, which represent a mixture of quartz (Qtz) and the metastable rosiaite-structured (Ros) high-pressure phase during compression. The densities of the individual phases have been inferred from measured lattice parameters and the proportions of the two phases were derived from Fig.

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Topological Ordering of Memory Glass on Extended Length Scales

“…In contrast, increasing the pressurization rate in the process of PIA does not necessarily promote amorphization. For instance, the archetypal quartz silica crystalizes into a disordered metastable d -NiAs-type phase via gas-gun shock compression to 65 GPa . Their experiment hints that the disordered phase has short-range and topological orderings, but it is neither a crystal nor an amorphous structure in nature.…”

“…For instance, the archetypal quartz silica crystalizes into a disordered metastable d-NiAs-type phase via gas-gun shock compression to 65 GPa. 48 Their experiment hints that the disordered phase has short-range and topological orderings, but it is neither a crystal nor an amorphous structure in nature. Shock compression generates pressure as well as heat.…”