polymorphic transition

https://doi.org/10.1351/goldbook.P04748
A @R05379@ of a solid crystalline phase at a certain temperature and pressure (the @I03149@) to another phase of the same chemical composition with a different crystal structure. Examples:
1. The transitions of SiO2 (quartz-type) at $$1143\ \text{K}$$ to SiO2 (tridymite-type), and at $$1743\ \text{K}$$ to SiO2 (cristobalite-type).
2. The transition of β-AgI (wurtzite-type structure) to α-AgI (body-centred-cubic structure) at $$418\ \text{K}$$. Synonymous with @E02084@.
Note:
In a liquid-crystal transition, this term refers to phase changes in the @S05714@ or columnar discotic state.
Source:
PAC, 1994, 66, 577. (Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)) on page 588 [Terms] [Paper]