Term: λ-transition (lambda-transition)
https://doi.org/10.1351/goldbook.T03420

Definition:
A second-order or higher-order transition, in which the heat capacity shows either a discontinuity (second-order) or a vertex (higher-order) at the transition temperature. Example: The transition at 846 K, accompanied by a finite change in specific heat capacity at constant pressure Cp, of the low-temperature polymorph of quartz to the high-temperature polymorph.

Related Terms:
1) second-order (http://doi.org/10.1351/goldbook.S05531).
2) higher-order transition (http://doi.org/10.1351/goldbook.H02822).
3) heat capacity (http://doi.org/10.1351/goldbook.H02753).
4) specific heat capacity (http://doi.org/10.1351/goldbook.S05800).

Source: PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 584 (https://doi.org/10.1351/pac199466030577)

Citation: 'λ-transition (lambda-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.T03420

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