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A mesoscale modelling study of nematic liquid crystals confined to ellipsoidal domains
Authors:Rishikesh K Bharadwaj  Timothy J Bunning  B L Farmer
Institution:1. Research Institute for Materials, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands;2. Universidade de Mogi das Cruzes, Av. Dr. C? andido X. A. Souza 200, CEP 08780-911, Mogi das Cruzes-SP-Brazil;3. Instituto de Física, Universidade de S?o Paulo, S?o Paulo, P.O. Box 66318, CEP 05315-970 Brazil;4. Instituto Nazionale di Fisica della Materia, Research Unit of Cosenza, Dipartamento di Fisica, Universita de la Calabria, 87036 Rende, Italy
Abstract:Director configurations of nematic liquid crystalline molecules packed in ellipsoidal domains have been investigated using mesoscale modelling techniques. Interactions between the directors were described by the Lebwohl-Lasher potential. Four different ellipsoidal shapes (sphere, oblate spheroid, prolate spheroid, and ellipsoid) were studied under homogeneous and homeotropic surface anchoring conditions. The model has been characterized by computing thermodynamic and structural properties as a function of ellipsoidal shape (prolate and oblate) and size. The predicted director configuration in ellipsoids resulting from homeotropic surface anchoring is found to be very different from that in spherical domains. The bipolar configuration involving homogeneous surface anchoring is nearly identical in the four cases. The effect of an external electric field, applied at different orientations with respect to the major axis of the ellipsoid, has been probed as a function of the magnitude of the field and the ellipsoidal size and shape. The orientation of directors is most easily accomplished parallel and perpendicular to the major axis for the oblate and prolate spheroids, respectively, for homeotropic anchoring, and along the bipolar symmetry axis for homogeneous anchoring. In domains with homeotropic surface anchoring, the oblate spheroid and elongated ellipsoid are predicted to be the most efficient geometries for PDLC applications; for homogeneous anchoring conditions, the prolate spheroid and elongated ellipsoid are predicted to be the most efficient.
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