A transition which involves a major reorganization of the crystal structure and a change of local topology, during which primary bonds are broken and reformed so that there is no immediate relationship between the crystal structures of the parent and product phases. Examples: The transition of Mg2SiO4
(olivine) to Mg2SiO4
(spinel); the transition of diamond to graphite.
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 589 (https://doi.org/10.1351/pac199466030577)