Prediction on the phase transform, optical and dielectric properties of liquid crystal molecule system by coarse grained molecular dynamics simulation and density functional theory calculation

• Main Authors: Sheng-Chieh Huang, 黃聖捷
• Other Authors: Ju, Shin-Pon
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/3u4cw7

碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 102 === We combine coarse grained (CG) molecular dynamics simulation and density functional theory (DFT) calculation to predict the phase behavior, the dielectric and the optical properties of liquid crystal molecule system. 4-Cyano-4′-pentylbiphenyl (5CB) is the earliest synthesized and the most popular liquid crystal molecule, which have prosperous related bibliographies and available experimental and theoretical data, so 5CB molecule is chosen to be the benchmark molecule. According to the Maier-Meier and Vuks equations, we have to obtain some parameters such as the dipole moment, the polarizability, the polarizability anisotropy, the order parameter and the molecular density to calculate dielectric and optical properties of liquid crystal molecule system. The CG model for the 5CB molecules is constructed, and the bond length, bending angle and nonbonded interaction parameters between CG beads, and then applied to the CGMD simulation to obtain the order parameter and molecular density. In addition, the polarizability and dipole moment of 5CB were obtained by DFT; therefore, the order parameter, the molecular density, the polarizability, and the dipole moment of 5CB were used to determine the dielectric constant, the dielectric anisotropy, refractive indices, and optical anisotropy by means of the Maier-Meier theory. Particularly, the calculation results from Maier-Meier theory can be improved by using effective dipole moment of the Dunmur-Palffy-Muhoray theory. Finally, our results show a good agreement with the experimental results, and it indicates that our simulation method is feasible and the results are accuracy.