A MEAN FIELD-THEORY OF DIPOLE DIPOLE CORRELATION IN NEMATIC LIQUID-CRYSTALS

A mean field theory of dipole-dipole correlation in nematic liquid crystals is developed by modelling the anisotropic radial distribution function for two hard ellipsoids. This, combined with a dipole-dipole interaction energy, allows the calculation of Kirkwood dipole correlation factors for uniaxial and biaxial particles. It is found that the Kirkwood correlation factors depend on the degree of orientational ordering, and the sense of the correlation as ferroelectric or antiferroelectric depends on the orientation of the molecular dipole with respect to the major geometric axis of the molecule. There is a symmetry between the results for rod-like and disc-like molecules, and the theoretical results are in qualitative agreement with recent experimental studies of dipole-dipole correlation.