Ultrafast X-Ray Diffraction Visualization of B1-B2 Phase Transition in KCl under Shock Compression

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• The B1(NaCl) to B2(CsCl) structural phase transition is a key model for understanding general phase transformations.
• Investigating these transitions under high strain rate shock compression is crucial for understanding phase transition dynamics.

Purpose of the Study:

• To elucidate the phase transition mechanisms of single-crystal potassium chloride (KCl) under planar shock compression.
• To utilize subnanosecond synchrotron X-ray diffraction for visualizing lattice response during dynamic compression.

Main Methods:

• Subnanosecond synchrotron X-ray diffraction
• Planar shock compression of single-crystal KCl
• Analysis of lattice response and orientation relations

Main Results:

• Complete B1-B2 orientation relations were observed for KCl shocked along ⟨100⟩_{B1} and ⟨110⟩_{B1}.
• The orientation relations and transition mechanisms were found to be anisotropic.
• Mechanisms involve interlayer sliding and intralayer ion rearrangement, describable by Watanabe-Tokonami-Morimoto models.

Conclusions:

• The study establishes a paradigm for investigating solid-solid phase transitions under dynamic extremes.
• Ultrafast synchrotron X-ray diffraction is a powerful tool for dynamic materials research.
• Anisotropic mechanisms govern KCl phase transitions under shock compression.