= Solution
\b[A <displacive transformation> changes structure through coordinated atomic displacements, whereas a <reconstructive transformation> changes the bonding/connectivity arrangement more substantially.]
In a displacive change, neighboring atoms move cooperatively without the long-range compositional redistribution characteristic of diffusion-controlled precipitation. The change can preserve many near-neighbor relationships and can occur rapidly when its kinetic conditions are met.
A reconstructive change requires breaking and re-forming the relevant structural connections to establish a different arrangement, often with a larger activation barrier and slower nucleation and growth. It may consequently show substantial kinetic persistence of a metastable phase. The distinction concerns the atomic mechanism, not merely whether the final phase has a different symmetry; neither label by itself supplies a universal transformation rate.
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