Molecular organization in liquids consisting of anisometric molecules: Monte Carlo simulations and comparison with theories

Abstract

Monte Carlo computer simulations of systems of rigid anisometric molecules with axial ratio x 3, 4 and 5 have been performed at densities comparable to those of the mesogenic groups in liquid crystalline materials. The agreement between computer experiments and Flory-Ronca-Irvine theory is quite good. In particular, the nematic-isotropic transition temperatures found in the simulations are within 20 K of those predicted by the theory in all cases examined with x 3 and 4, and only slightly higher when x 5. Furthermore, the orientational distributions of the molecular long axes with respect to the nematic director are always nearly coincident with those evaluated according to the FRI theory, 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 performed by changing the size of the simulated systems prove that the reported results are size independent, while size dependent results are obtained with smaller systems.