https://doi.org/10.1351/goldbook.D01733
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:
- The transition of a $\ce{CsCl}$-type structure to a rock salt structure in which dilation occurs along the three-fold axis.
- The transition at \(T_{\rm{D}}\) in quenched $\ce{NiS}$ in which volume expansion occurs without change of symmetry on going from a metallic state (\(T > T_{\rm{D}}\)) to a semiconducting state (\(T < T_{\rm{D}}\)).