Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
J Phys Chem B. 2011 Mar 17;115(10):2214-27. doi: 10.1021/jp111408n. Epub 2011 Feb 22.
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.
液晶在材料科学中起着至关重要的作用，在纳米技术和工业中显示出越来越多的潜在应用。一般来说，液晶的热力学和动力学性质强烈依赖于相应的力场（FF）；因此，为给定的液晶系统建立一个可靠的力场是必要的和紧迫的。在本文中，我们通过重新优化 TraPPE-UA 的一些参数来为 5CB（4-氰基-4'-戊基联苯）分子开发了一组新的 FF 参数，以再现体密度。这种构建 5CB FF 的策略是相当明智的，因为它不仅为 Lennard-Jones 参数提供了可靠的值，而且降低了计算成本并保持了 FF 的可转移性。事实上，我们的模拟结果表明，5CB 的相行为、有序参数、构象特征、相邻分子对排列和扩散性质可以得到很好的再现。我们通过将其扩展到 8CB（4-氰基-4'-辛基联苯）系统进一步验证了这种 5CB FF 的可转移性。结果，8CB 的向列相和部分双层向列相（Sm-A(d)）以及向列-各向同性和向列-向列相变温度以及扩散性质都得到了成功再现。因此，这套最初为 5CB 分子设计的 FF 参数是可靠和可转移的。预计它将有效地用于模拟 nCB 系列和具有类似化学结构的分子。
