ELASTIC-CONSTANTS OF NEMATIC LIQUID-CRYSTALS FROM MOLECULAR-DYNAMICS SIMULATIONS

The Frank-Oseen elastic constants K-11, K-22 and K-33 as well as the s urface constants K-13 and K-24 have been calculated for Gay-Berne nema tic liquid crystal with anisotropy parameters k = 3 and k' = 5. In der iving the elastic constants a direct correlation func tion approach of Poniewierski and Stecki(1) in a version proposed by Lipkin et al.(5) was choosen. The final formulas have been expressed in terms of the or ientational order parameters and of the angular coefficients of the di rect correlation function of an unoriented nematic. The latter have be en determined exactly from the molecular dynamics simulations in the N VT ensemble. Results for the surface elastic constants, qualitatively different than those obtained from all previous treatments, clearly sh ow that the surface deformations are strongly sensitive to details of the direct correlation function. Obtained values of surface elastic co nstants are partly negative and an order of magnitude smaller than bul k elastic constants.