PRETRANSITIONAL FLUCTUATIONS OF THE LEBWOHL-LASHER MODEL OF A NEMATIC LIQUID-CRYSTAL

We carry out Monte Carlo simulations of the Lebwohl-Lasher model of a nematic liquid crystal at temperatures just above the orientational ordering transition. We calculate the correlation functions for the order parameter fluctuations which are compared to the predictions of Landau theory in the Gaussian approximation in order to infer the values of the inverse susceptibility A and the elastic constant L. We also observe the distribution function for the invariant trQ2, which has simple analytic form if the fluctuations of the order parameter have a Gaussian distribution. At those temperatures for which the distribution of order parameter fluctuations is Gaussian, A is found to follow the Landau theory behavior A(T) = a(T - T*), with (T(c) - T*)/T(c) = 3 x 10(-3), where T(c) is the nematic-isotropic phase transition temperature.