Theory of dielectric anisotropy

As an example of an application of the mean field method we shall consider the theory of the dielectric anisotropy of the nematic phase. The low frequency dielectric anisotropy of a molecule is determined by two factors (i) the polarizability anisotropy which for the elongated molecules of nematogenic compounds always makes a positive contribution (i.e., a 

In contrast to diamagnetism where the magnetic interactions between molecules can be neglected, the polarization field in the medium becomes important when discussing dielectric anisotropy (see, e.g., Bottcher ). Maier and Meier took this into account by applying the Onsager theory.The effective induced dipole moments per molecule along and 

To calculate the effective permanent dipole moment, we choose XYZ as the space-fixed coordinate system, Z being parallel to the unique axis of the medium, and as the molecule-fixed coordinate system, the axis coinciding with the long axis of the molecule. Let v be the Eulerian angle between the axis and the line of intersection of the XY and planes, and 

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