Title: subgroup-supergroup transition
Long Title: IUPAC Gold Book - subgroup-supergroup transition
DOI: 10.1351/goldbook.S06066
Status: current

Definition
A transition in which the space-group symmetry of the lower symmetry phase is a subgroup of that of the higher symmetry phase. Example: The transition of the low-temperature polymorph of quartz characterized by space-group symmetry \(P3_{1}2\) (trigonal), to the high temperature polymorph of quartz with space-group symmetry, \(P6_{2}22\) (hexagonal). Synonymous with 'symmetry-breaking transition' (note: this term, strictly speaking, is no longer in use).

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)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/S06066/html
- json: https://goldbook.iupac.org/terms/view/S06066/json
- xml: https://goldbook.iupac.org/terms/view/S06066/xml

Citation: Citation: 'subgroup-supergroup transition' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.S06066
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Accessed: 2026-06-20T04:46:14+00:00