dilational transition (dilatational transition)

A transition in which the crystal structure is dilated (or compressed) along one (or more) crystallographic direction(s) while the symmetry about that direction is retained. Examples:
  1. The transition of a CsCl-type structure to a rock salt structure in which dilation occurs along the three-fold axis.
  2. The transition at T D in quenched NiS in which volume expansion occurs without change of symmetry on going from a metallic state (T > T D) to a semiconducting state (T < T D).
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 581 (https://doi.org/10.1351/pac199466030577)