MOLECULAR-ORGANIZATION IN LIQUIDS CONSISTING OF ANISOMETRIC MOLECULES- MONTE-CARLO SIMULATIONS AND COMPARISON WITH THEORIES

Monte Carlo computer simulations of systems of rigid anisometric molec ules with axial ratio x = 3, 4 and 5 have been performed at densities comparable to those of the mesogenic groups in liquid crystalline mate rials. The agreement between computer experiments and Flory-Ronca-Irvi ne theory is quite good. In particular, the nematic-isotropic transiti on temperatures found in the simulations are within 20 K of those pred icted by the theory in all cases examined with x = 3 and 4, and only s lightly higher when x = 5. Furthermore, the orientational distribution s of the molecular long axes with respect to the nematic director are always nearly coincident with those evaluated according to the FRI the ory, provided that the order parameter is the same. However, the order parameters at the transition points are smaller than expected on the basis of the theory, and closer to experimental values. Calculations p erformed by changing the size of the simulated systems prove that the reported results are size independent, while size dependent results ar e obtained with smaller systems.