Flexoelectric Effects in Liquid Crystals Formed by Pear Shaped Molecules. A Computer Simulation Study

where e11 and e33 denote the flexoelectric coefficients related to splay and bend distortions, respectively. The phenomenon is somewhat similar to the piezoelectric effect in certain solid crystals where a coupling between mechanical stress and polarization is observed, so that the polarization manifests itself due to a positional deformation. The flexoelectric effect has attracted a great deal of attention because of its possible applications in transducers and, generally, in electro-optical devices. However, and more importantly here, there is also a fundamental interest, as the relation between the flexoelectric coefficients and molecular structure is far from being understood. Meyer in his seminal paper [1] showed that a geometrical asymmetry of the mesogen molecules, or “shape polarity”, should lead to a non vanishing effect. He used as explicit examples wedge-shaped (“pear”) and bow-shaped (“banana”) molecules. These are of course not the only molecular shapes allowing the effect and Prost and Marcerou [2,3] and Osipov [4,5], in particular, have considered quadrupolar-like flexoelectricity. From the theoretical point of view microscopic theories of the effect have