Jahn–Teller transition

A displacive crystal distortion to lower symmetry that cooperatively removes a localized-electron orbital degeneracy at an array of like atoms so as to leave the atoms in the centre of symmetry of their distorted sites. Example: The crystallographic distortion in Mn3O4.
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 584 (https://doi.org/10.1351/pac199466030577)