Liquid crystals playing a crucial role in material sciences show increasing potential applications in nanotechnology and industry. Generally, thermodynamic and dynamic properties of liquid crystals strongly depend on the corresponding force fields (FF); thus, it is necessary and urgent for us to establish a reliable force field for a given liquid crystal system. In this paper, we develop a new set of FF parameters for the 5CB (4-cyano-4'-pentylbiphenyl) molecule by reoptimizing some parameters of TraPPE-UA in order to reproduce the bulk density. This strategy for the construction of 5CB FF is rather advisable as it not only provides reliable values for the Lennard-Jones parameters but also reduces the computational cost and maintains FF transferability. Indeed, our simulation results show that the phase behavior, the order parameter, conformational features, neighboring molecular pair arrangements, and diffusion properties of 5CB can be reproduced very well. We further validate the transferability of this 5CB FF by extending it to the 8CB (4-cyano-4'-octylbiphenyl) system. As a result, both the nematic and the partial bilayer smectic phases (Sm-A(d)) and the nematic-isotropic and the smectic-nematic transition temperatures as well as the diffusion properties of 8CB are successfully reproduced. Therefore, this set of FF parameters originally designed for the 5CB molecule is reliable and transferable. Its effectiveness to model nCB series and molecules with similar chemical structures is expected.
© 2011 American Chemical Society