The threshold potentials for different types of electric Freedericksz transitions are calculated from the free energy density expression for nematics in an external electric field derived by the present authors.[1] It is found that the experimentally determined elastic constants should be replaced by the effective elastic constants. With the effective elastic constants some of the discrepancies between earlier theoretical calculations and experimental data can be explained qualitatively.
Accepting that a macroscopic physical quantity may be considered as the statistical average of the corresponding molecular physical quantity, we present in this paper the eKpressions of all the nonvanishing fourth order tensor y.±jkl w ith Dooft symmetry associated with nematic liquid crystals•in terms of the corresponding molecular fourth order tensors ^'ijkl and the order parameters S 3 and Si,.
It is well known, that planar nematic liquid crystal cells with tilted director on the boundaries have no threshold field for magnetic Freedericksz transition. However, it is found that if one arranges the two glass plates of the cell such that the tilt angle of the director on one plate is opposite to that on the other, the same threshold magnetic field as in a cell with ideal initial orientation will be observed. It is found also that for a wedge-shaped cell with ideal initial orientation the threshold field will be lower than that for a planar cell.
In this paper we show analytically that, in general, nematic liquid crystals (NLC) with curvature strain belong to the C\[l] point group. However, NLC with simple splay deformation or simple bend deformation possess C2 v [mm2] symmetry and those with simple twist deformation possess Dz[222] symmetry.
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