For the cubic lattices of the liquid-crystalline blue phases I and II electrostriction has been observed recently, i.e., a distortion of the crystal by an electric field in quadratic order. Here we investigate the characterizing fourth-order electrostriction tensor. Because electrostriction results from a competition between electric and elastic forces, the tensor is the quotient of the elasto-optic and the elastic tensor. The latter are derived from the Landau–de Gennes theory of phase transitions in liquid crystals within the model of rigid helices and are expressed as functionals of the alignment tensor for the undistorted system. Comparison is made with experimental data. The limitations of the model of rigid helices are discussed.

• Received 18 March 1991

DOI:https://doi.org/10.1103/PhysRevA.44.2752