Nanosecond structural evolution in shocked coesite

Area of Science:

• Mineral physics
• Geochemistry
• Materials science

Background:

• Shock-induced phase transitions in minerals are key to understanding impact events.
• Previous studies on shocked silica at 65 GPa suggested complex high-pressure phases.
• Silica's behavior under extreme pressure, especially during superheating before melting, requires further investigation.

Purpose of the Study:

• To investigate the time-dependent response of coesite under laser-driven shock.
• To explore the complex phase evolution pathways of silica under high pressure.
• To provide insights into silica phases found in extraterrestrial impact events.

Main Methods:

• Laser-driven shock experiments.
• Time-resolved X-ray diffraction (XRD) for in-situ analysis.
• Molecular dynamics simulations utilizing a novel machine learning interatomic potential.

Main Results:

• Observed a transient dense supercooled liquid silica.
• Identified crystallization into a semi-disordered d-NiAs-type silica.
• Documented transformations to seifertite or stishovite, pressure-dependent.
• Revealed a back-transformation to coesite upon pressure release, not quartz.

Conclusions:

• Shocked coesite exhibits intricate phase evolution pathways.
• The observed phases and transformations enhance understanding of silica behavior under extreme shock conditions.
• Findings contribute to interpreting high-pressure silica phases in meteorite impact records on terrestrial planets.