Influence of surface elasticity on the director profile of nontwisted nematic-liquid-crystal cells

The Pergamenshchik theory [Phys. Rev. E 48, 1254 (1993)] and Faetti theory [Phys. Rev. E 49, 5332 (1994); 49, 4192 (1994)] of surface elasticity in nematic liquid crystals are tested. Both theories give different predictions concerning the influence of the splay-bend surface elastic constant K₁₃ on the director profile of nontwisted liquid-crystal cells. The influence of K₁₃ on the director profile of nontwisted liquid-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, Germany) are measured as a function of the applied voltage. The surface tilt as a function of the applied voltage is calculated from these data and compared with numerically calculated curves. The model does not give a complete account of the observed optical behavior. Best agreement with the capacitive measurements is obtained with K₁₃=0. The effect of K₁₃ is comparable in magnitude with the effect of variations of the bulk liquid-crystal parameters within their experimental inaccuracy. {} 1996 The American Physical Society.