second-order transition

Synonym: continuous transition
A transition in which a crystal structure undergoes a continuous change and in which the first derivatives of the Gibbs energies (or chemical potentials) are continuous but the second derivatives with respect to temperature and pressure (i.e. @H02753@, thermal expansion, compressibility) are discontinuous. Example: The @O04321@ in metal alloys, for example, CuZn. Synonymous with continuous transition.
PAC, 1994, 66, 577. (Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)) on page 589 [Terms] [Paper]