Second-Order Phase Transitions

Abstract

This chapter treats the thermodynamic and group theoretical techniques useful in the consideration of phase transitions which occur without the coexistence of two phases, i.e., without the nucleation and growth of a new phase. The transitions under consideration occur with a change of symmetry at a certain thermodynamic state during a continuous structure change through that state. Such structure changes may be of three types: order-disorder, displacive and a combination of order-disorder and displacive. In the latter case the ordering is incommensurate with the translational periodicity of the lattice, as will be shown in a later section.