Author/Editor		Žekš, B; Čepič, M
Title		Ferro- and antiferroelectric liquid crystals: modelling of ferroelectric and antiferroeletric liquid crystals
Type		članek
Source		In: Haase W, Wrobel S. Relaxation phenomena: liquid crystals, magnetic systems, polymers, high-Tc superconductors, metallic glasses. Berlin: Springer,
Publication year		2003
Volume		str. 257-74
Language		eng
Abstract		A short historical overview of the development of phenomenological models of ferroelectric and antiferroelectric liquid crystals is given: For a theoretical modeling of the ferroeleetric liquid crystals the tilt order parameter and the polarization order parameter are needed. The free energy is expressed in both order parameters and only small changes of both order parameters from the layer to the layer are allowed. Description is therefore sometimes also called continuous. After discovery of the antiferroelectric liquid crystals, the phenomenological model for the ferroelectric liquid crystals has been extended to systems with a double layer periodical structures by introduction of the ferroelectric and antiferroelectric tilts and polarizations. The model allow for some of the phases but fails to predict phases with periodical structures with periods longer than two layers. Discrete models where inter-layer interactions are taken into account explicitly, allow for more complex structures with three-, four- and more layer in general incommensurate periodicities. Various microscopic interactions and their phenomenological description as well as the link between the terms in the continuous and discrete description is discussed. The general free energy for a smectic liquid crystal that consists of chiral molecules is presented, and the typical phase sequence including the structures of the stable phases is briefly analyzed.
Descriptors		BIOPHYSICS CRYSTALLIZATION MODELS, THEORETICAL