https://doi.org/10.1351/goldbook.A00244
A transition of a pure element, at a defined temperature and pressure, from one crystal structure to another which contains the same atoms but which has different properties. Examples: The transition of @G02684@ to @D01671@, that of body-centred-cubic iron to face-centred-cubic iron, and the transition of orthorhombic sulfur to monoclinic sulfur.