Gyrotropic phase transitions

Structural (gyrotropic) phase transitions from optically inactive to optically active (gyrotropic) phases are analysed for nonmagnetic materials. The following basic results of group theoretical analysis are gathered for those equitranslational gyrotropic phase transitions which are associated with a single REP (irreducible or physically irreducible representations): e.g. the macroscopic transition parameter, the spontaneous components of the gyration tensor, the polarisation and deformation tensors newly onsetting at the transition, the indices of faintness, faint interactions, and switching forces. A simple characterisation of the domain structure of the ferroic phase is given in terms of these tensors.