Parameterization of the Gay-Berne potential for nCB

Abstract

To study the effect of the alkyl chain on the liquid crystalline phase of nCB (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 rigid part (4-methyl-4'-cyanobiphenyl moiety; CB), and a flexible part represented 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 averaged over the rotation of CB around the axis of the ellipsoid. The resulting 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 potential was validated by MD simulations for 1CB and 5CB.