Parameterization of the Gay-Berne potential for nCB

To study the effect of the alkyl chain on the liquid crystalline phase of n CB (4-n-alkyl-4'-cyanobiphenyl) by molecular dynamics (MD) simulations, we have determined a coarse-grained potential for nCB based on the united atom potential by the OPLS force field. An nCB molecule was divided into a rigi d part (4-methyl-4'-cyanobiphenyl moiety; CB), and a flexible part represen ted by a chain of united atoms (UA's). In order to approximate the CB part as an ellipsoid, the OPLS potential between the CB-CB (or CB-UA) pair was a veraged over the rotation of CB around the axis of the ellipsoid. The resul ting potential surface was fitted into the Gay-Berne (GB) potential between two ellipsoids (or between an ellipsoid and a sphere). The UA-UA potential was assumed to be the same as the original OPLS potential. The obtained po tential was validated by MD simulations for 1CB and 5CB.