Elastic and flexoelectric properties of chiral smectic-C phase and symmetry considerations on ferroelectric liquid-crystal cells

Abstract

The elastic energy expression of de Gennes for the non-chiral and chiral smectic-C phases is reformulated, and it is shown that the maximum size of a uniformly oriented sample is limited, not only by the chiral helix but also by a spontaneous bend of the smectic layers. A description of the flexoelectric effects is given: 9 different vector fields are involved, and they all remain in non-chiral smectic-C phase. These vector fields are connected to the divergence terms in the elastic free energy. The complexity of the boundary conditions for ferroelectric liquid crystals is discussed, and the concepts ‘bookshelf geometry’ and ‘φ-can’ are introduced. It is shown how the φ-can may be used to describe various monostable and bistable configurations of smectic-C cells. The symmetry of the cell can determine the configuration. Some general rules concerning the optical behaviour of smectic-C cells are given.