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Geological Sciences Seminar: Sally Tracy, Carnegie Institute for Science

Tuesday, May 11, 2021 12:00 PM
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Faculty/Staff, Students, Alumni/Friends
Department of Geological Science

X-ray diffraction studies of mineral phase transitions under shock loading

Laboratory shockwave experiments have long played an important role in Earth and planetary science. Shock loading provides a powerful means of measuring equations of state and phase transitions at the high pressure-temperature conditions of planetary interiors. Furthermore, the characterization of shock-compressed minerals is critical for understanding shock metamorphism in samples from meteorites and natural impact sites. However, an historical limitation of shockwave studies has been that the in situ crystal structure of the high-pressure phase formed on compression is generally not known. Breakthrough capabilities combining dynamic compression with pulsed X-ray probes have enabled the investigation of crystallographic phase transformations as they occur in real-time during a shock event. New experiments can address a range of long-standing questions including: what phases are stable under what conditions, what is their thermoelastic behavior, when do they melt or vaporize, and what phases will form on release? This talk will review recent in situ diffraction studies of silicates and carbonates under gas-gun and laser-based shock compression. These studies demonstrate that high-pressure phase transitions can be explored on nanosecond timescales, improving our understanding of minerals at the extreme conditions of planetary interiors and impact events.

Sally June Tracy is a Staff Scientist at the Carnegie’s Earth and Planets Laboratory. Tracy received her Ph.D. in Materials Science from Caltech in 2016. After a postdoctoral fellowship in the Department of Geosciences at Princeton University, she joined Carnegie in 2019. Tracy is interested in and for exploration of novel materials in extreme conditions. Her research spans mineral physics and materials science. She uses both static and dynamic compression techniques coupled with high-flux X-ray sources to probe structural deformation and phase transitions in materials at conditions relevant for impacts and the interiors of terrestrial and exoplanets

Email Kelly Wells,, for Zoom link and password.

2019 Webby Award Nominee

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