Phenomenological Theory of the Antiferroelectric Nematic to Antiferroelectric Smectic-A Phase Transition

Recent experiments on the binary mixtures of two ferroelectric liquid crystals compounds showed the existence of antiferroelectric nematic (N AF ) and antiferroelectric smectic-A (SmA AF ) phases. In this work, N AF to SmA AF phase transition has been studied on the basis of phenomenological theory. The model free energy is written in terms of the orientational order parameter, translational order parameter and spontaneous polarization. Different types of phase sequences, including the N AF and SmA AF phases have been discussed. A detailed analysis has been presented to describe different phases that can occur. The stability conditions of the N AF and SmA AF phases have been discussed. On the basis of this model, a variety of phase transitions, including the N AF –SmA AF phase transition has been identified.