A jumping crystal predicted with molecular dynamics and analysed with TLS refinement against powder diffraction data

Area of Science:

• Solid-state chemistry
• Crystallography
• Computational materials science

Background:

• Understanding phase transitions in crystalline materials is crucial for materials design.
• The 'jumping crystal' phenomenon presents a unique case for studying solid-state dynamics.
• The high-temperature phase structure and transition mechanism were previously unknown.

Purpose of the Study:

• To elucidate the phase transition mechanism in a 'jumping crystal'.
• To predict and verify the crystal structure of the high-temperature phase.
• To investigate the role of molecular motion in driving the phase transition.

Main Methods:

• Performing temperature-dependent molecular dynamics (MD) simulations.
• Analyzing unit-cell parameters and anisotropic displacement parameters.
• Experimental validation using X-ray powder diffraction and Translation, Libration, Screw (TLS) refinement.

Main Results:

• The MD simulations successfully captured the experimentally observed phase transition.
• A discontinuity in two unit-cell parameters was observed during the transition.
• Libration was identified as the primary driving force for the phase transition.
• The predicted high-temperature crystal structure was confirmed experimentally.

Conclusions:

• Molecular dynamics simulations are effective for predicting phase transitions and structures.
• The phase transition in the 'jumping crystal' is driven by anisotropic molecular libration.
• Experimental verification confirmed the computational predictions, advancing the understanding of this material.