A Molecular Statistical Calculation of Pretransitional Effects in Nematic Liquid Crystals

Abstract

A molecular statistical treatment is given of two pretransitional effects in the isotropic phase of nematic liquid crystals, namely of the magnetically induced birefringence and the scattering of light by orientational fluctuations. The calculations are based on the Maier-Saupe model, treated in teh Bethe approximation in order to account for short range order. The ratio (T _e - T _c∗)/T _c is improved considerably with respect to the mean field approximation. Also the cluster variation method is applied to the Maier-Saupe model. The differences between the results of the Bethe and the cluster variation method are discussed. A slight modification of the Bethe method produces close agreement with the cluster variation method.