Direct Observations of a Dynamically Driven Phase Transition with in situ X-Ray Diffraction in a Simple Ionic Crystal

Area of Science:

• High-pressure physics
• Materials science
• Solid-state chemistry

Background:

• Calcium fluoride (CaF2) serves as a model AB2 structure for studying phase transitions.
• Understanding phase transitions in ionic solids is crucial for materials science and geophysics.

Purpose of the Study:

• To investigate the real-time kinetics and hysteresis of the fluorite to cotunnite structural phase transition in CaF2.
• To provide insights into the transition mechanisms under dynamic and static compression.

Main Methods:

• In situ synchrotron X-ray diffraction.
• Dynamic loading up to 27.7 GPa.
• Static compression.
• Rietveld refinement techniques.

Main Results:

• Real-time observations of the fluorite to cotunnite phase transition were achieved.
• The kinetics and hysteresis of the transition were examined on nanosecond and minute timescales.
• Data provides insight into the kinetic time scale of the transition under shock compression.

Conclusions:

• The study elucidates the dynamic behavior of the CaF2 phase transition.
• Findings are relevant to isomorphic compounds and high-pressure physics applications.
• Real-time diffraction offers a powerful tool for studying rapid material transformations.