Elastic constants from direct correlation functions in nematic liquid crystals: A computer simulation study

Density functional theories such as the Poniewierski-Stecki theory relate t he elastic properties of nematic liquid crystals with their local liquid st ructure, i.e., with the direct correlation function (DCF) of the particles. We propose a way to determine the DCF in the nematic state from simulation s without any approximations, taking into account the dependence of pair co rrelations on the orientation of the director explicitly. Using this scheme , we evaluate the Frank elastic constants K-11, K-22, and K-33 in a system of soft ellipsoids. The values are in good agreement with those obtained di rectly from an analysis of order fluctuations. Our method thus establishes a reliable way to calculate elastic constants from pair distributions in co mputer simulations. (C) 2001 American Institute of Physics.