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

Area of Science:

• Geophysics
• Materials Science
• Mineral Physics

Background:

• Quartz (SiO2) is crucial in geophysics and materials science, extensively studied under dynamic compression.
• Previous research suggests quartz transforms to a dense high-pressure phase under shock loading, often assumed to be stishovite.
• However, direct crystal structure data for shock-compressed quartz has been lacking.

Purpose of the Study:

• To determine the crystal structure of shock-compressed α-quartz.
• To investigate phase transformations of SiO2 under dynamic compression up to 65 GPa.
• To challenge existing assumptions about quartz's high-pressure behavior.

Main Methods:

• Utilized gas-gun shock compression.
• Employed in situ synchrotron X-ray diffraction for real-time structural analysis.
• Examined α-quartz samples subjected to shock pressures up to 65 GPa.

Main Results:

• Observed a phase transformation in shock-compressed α-quartz.
• The resulting high-pressure phase is disordered and metastable.
• This phase is neither crystalline stishovite nor amorphous SiO2.

Conclusions:

• The dynamic compression of quartz does not lead to the stishovite phase as previously assumed.
• A novel disordered metastable phase of SiO2 is formed under shock conditions.
• This discovery necessitates a re-evaluation of quartz's behavior under extreme dynamic pressures.