ELECTRIC-FIELD-INDUCED DIRECTOR-FIELD TRANSITION OF NEMATIC LIQUID-CRYSTAL IN A CLOSED CONICAL CAVITY

Continuum theory and numerical method are utilized in this study to report the dependence of director-field transition induced by electric field on the elastic constants of nematic liquid crystal (NLC) with negative dielectric anisotropy in a closed conical cavity with perpendicular boundary conditions of NLC. Normal umbilic structure (NU), twisted umbilic structure (TU), normal hyperbolic point structure with a disclination ring (NH), twisted hyperbolic point structure with a disclination ring (TH), and normal Poincare structure (NP) are found to be stable structures in electric-field-induced transitions. Moreover, five typical sequences of transition, T-NU-->TU-->TH, T-NU-->TU-->NH-->TH, T-NU-->TU-->NH, T-NU-->NH, and T-NU-->NP-->NH are found in the range of applied voltage less than 10 V. The transition sequences and the transition voltages are strongly dependent on the ratios of elastic constants K-11/K-33 and K-22/K-33.