## Wikipedia - Polymorphism (materials science) (en) Wikipedia - Selen (de) Wikipedia - Substância (pt) polymorphic transition

https://doi.org/10.1351/goldbook.P04748
A @[email protected] of a solid crystalline phase at a certain temperature and pressure (the @[email protected]) 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 @[email protected]
Note:
In a liquid-crystal transition, this term refers to phase changes in the @[email protected] 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]