A transition that requires the
rearrangement of atoms, ions or molecules in a manner that cannot be accomplished by a cooperative atomic displacement; it may require the movement of atoms, ions or molecules over distances significantly larger than a
unit cell. Example: The transition of
graphite (hexagonal sheets of three-coordinated carbon atoms) to
diamond (infinite three-dimensional framework of four-coordinated carbon atoms) at high temperature and pressure.
Source:
PAC, 1994, 66, 577
(Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994))
on page 581