Prediction of Optical and Dielectric Properties of 4-Cyano-4-pentylbiphenyl Liquid Crystals by Molecular Dynamics Simulation, Coarse-Grained Dynamics Simulation, and Density Functional Theory Calculation

Abstract

The Maier−Meier theory and Vuks theory were used to obtain the dielectric anisotropy and birefringence of the 4-cyano-4-pentylbiphenyl (5CB) liquid crystal system for a benchmark. The molecular dynamics (MD) simulation, coarsegrained molecular dynamics (CGMD) simulation, and the density functional theory (DFT) calculation were used to get the required parameters of the Maier−Meier theory and Vuks theory. The molecular density obtained by the MD simulation is about 1.05 g/cm 3 , which is very close to the available experimental value of 1.008 g/cm 3 . In the CGMD simulation, the order parameter is about 0.44 for the 5CB conformation at the temperature that the transformation from the nematic to disorder arrangement occurs. The polarizability (α), polarizability anisotropy (Δα), and dipole moment (μ) of a 5CB molecule were obtained by the DFT calculation with the functional of B3LYP/6-31+G(2d,p). With these parameters, the birefringence of 5CB by the Vuks theory is very close to the experimental value with the error under 1%, but the dielectric constant and dielectric anisotropy by the Maier−Meier theory display the considerable errors higher than the corresponding experimental data by 218% and 260%, respectively. With the further concern about the Kirkwood's correlation factor for the effective dipole moment, the dielectric constant and dielectric anisotropy errors decrease from 218% to 12% and from 260% to 2%, respectively. From these results, it shows the dielectric anisotropy and the birefringence of a liquid crystal system can be accurately predicted by the Maier−Meier theory and Vuks theory with the parameters from the MD, CGMD, and DFT calculation as well as considering the effective dipole moment.

Synthesis of liquid crystals bearing 1,3-dioxane structures and characterization of their ferroelectricity in the nematic phase

“…To understand the emergence of the N F phases, we performed the quantum chemical calculations of C3-DIO analogues and evaluated the relationships between their structural parameters and the emergence of N F phases. The most stable geometries and dipole moments of these molecules were calculated using density functional theory (DFT) calculation with B3LYP/6-31+G(2d,p) basic functions as previously reported, 26,27 and their structural parameters and dipole moment are summarized in Table 2.…”

Multiscale Study of the Relationship between Photoisomerization and Mechanical Behavior of Azo-Polymer Based on the Coarse-Grained Molecular Dynamics Simulation

“…Table lists the deviations of the RDF and density of the CG systems from those of the AA MD unit cells. The precisely refined potential sets derived in this study yield considerably small relative errors compared with those computed in other publications. , …”

“…The precisely refined potential sets derived in this study yield considerably small relative errors compared with those computed in other publications. 35,39 Generally, the CG pair interactions are constructed using two different methods: deriving the numerically tabulated functions or adjusting the parameters of typical analytic forms such as the Lennard-Jones (LJ) or Morse potentials. Although the latter method is simpler and more practical, using the standardized forms causes difficulties in describing the complex anisotropic interactions between the LC molecules.…”

A Comparative Study on Electro-Optic Effects of Organic N-Benzyl-2-Methyl-4-Nitroaniline and Morpholinium 2-Chloro-4-Nitrobenzoate Doped in Nematic Liquid Crystals E7

“…The parameters such as polarizability ( α ), polarizability anisotropy (Δ α ), dipole moment ( μ ), absorbance spectra, highest occupied molecular orbital (HOMO), and lowest unoccupied molecular orbital (LUMO) of the LC mixture can be obtained from the optimized geometries. Subsequently, the change in Δ ε of the LC mixture can be deduced with Maier-Meier Equations (1)–(3) [ 29 ]. where Δ ε is defined as the difference between the permittivity parallel ( ε ∥ ) and perpendicular ( ε ⊥ ) to the molecular axis at 1 kHz; N is the molecular number density; ε 0 is the vacuum permittivity; K b is the Boltzmann constant; F and h are the reaction field factor and the cavity factor, respectively; θ is the dipole moment orientation angle relative to the long principal axis.…”