Term: rotator phase transition
https://doi.org/10.1351/goldbook.R05414

Definition:
A transition from a fully-ordered crystal of globular or quasi-spherical molecules to a crystal that retains translational order but exhibits dynamic orientational disorder and is usually mechanically soft (plastic phase). Example: The transition of CBr4 to a plastic phase which exists from 319 to 365 K.

Source: PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 589 (https://doi.org/10.1351/pac199466030577)

Citation: 'rotator phase transition' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.R05414

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