monotropic transition

https://doi.org/10.1351/goldbook.M04028
The irreversible transition from a metastable polymorphic form to the stable polymorph. Example: The transition of metastableCaCO3 (aragonite-type) to the stableCaCO3 (calcite-type).
Note:
For liquid crystals the term refers to a @LT06856@ to @L03579@ that occurs below the @M03821@ point and is revealed by supercooling of the crystal.
Source:
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 586 (https://doi.org/10.1351/pac199466030577)