Term: structural transition https://doi.org/10.1351/goldbook.S06062 Definition: A reversible or irreversible transition that involves a change of the crystal structure. Example: The transition of NH4Cl at 469 K from a CsCl-type structure to a NaCl-type structure. Related Terms: 1) reversible (http://doi.org/10.1351/goldbook.R05379). 2) irreversible transition (http://doi.org/10.1351/goldbook.I03258). Source: PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 591 (https://doi.org/10.1351/pac199466030577) Citation: 'structural 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.S06062 License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.