INFLUENCE OF SURFACE ELASTICITY ON THE DIRECTOR PROFILE OF NONTWISTEDNEMATIC-LIQUID-CRYSTAL CELLS

The Pergamenshchik theory [Phys. Rev. E 48, 1254 (1993)] and Faetti th eory [Phys. Rev. E 49, 5332 (1994); 49, 4192 (1994)] of surface elasti city in nematic liquid crystals are tested. Both theories give differe nt predictions concerning the influence of the splay-bend surface elas tic constant K-13 on the director profile of nontwisted liquid-crystal cells. The influence of K-13 on the director profile of nontwisted li quid-crystal cells is studied numerically within the framework of the Pergamenshchik theory. The capacitance and optical retardation of thin cells filled with the liquid crystal ZLI 4792 (E. Merck, Darmstadt, G ermany) are measured as a function of the applied voltage. The surface tilt as a function of the applied voltage is calculated from these da ta and compared with numerically calculated curves. The model does not give a complete account of the observed optical behavior. Best agreem ent with the capacitive measurements is obtained with K-13 = 0. The ef fect of K-13 is comparable in magnitude with the effect of variations of the bulk liquid-crystal parameters within their experimental inaccu racy.