Investigating the Calculation of Rotational Viscosity of the Mixture Comprising Different Kinds of Liquid Crystals: Molecular Dynamics Computer Simulation Approach

Abstract

Molecular dynamics (MD) computer simulation techniques, as a powerful tool commonly utilized by the liquid crystal display (LCD) community, usually are employed for computing the equilibrium and transport properties of a classical many body system, since they are very similar to real experiments in many respects. In this paper we present molecular dynamics computer simulation results taken for a mixture of the two different kinds of nematic liquid crystals (LCs). We calculated rotational viscosity from Brownian behavior with friction of the mean director of the mixture comprising pentylcyanobiphenol (5CB) and decylcyanobiphenol (10CB) by using molecular dynamics computer simulation, where intermolecular potential parameter is Generalized AMBER force field (GAFF). Our computed results show a good agreement with the experimental results.

Rotational viscosity calculation method for liquid crystal mixture using molecular dynamics

“…The duration of the step that involved the equilibration of the temperature for the canonical ensemble (NVT) was increased slightly from before the study, from 0.1 to 0.15 ns [13]. The equilibrium MD used the isothermal-isobaric ensemble (NPT).…”

“…The rotational viscosity of a mixture of 5CB and decylcyanobiphenol (10CB) was calculated in 2009 [9][10][11][12][13]. It was the first time the rotational viscosity of a mixture of different kinds of LCs was calculated [10,13].…”

“…The overall methodology comprises molecular geometry optimization and charge calculation using the Gaussian ab initio calculation, the MD computer simulation of an LC * Corresponding author. Email: yjjeon@konkuk.ac.kr mixture, and numerical analysis [10,13]. Some parameters of the Gaussian ab initio calculation were modified.…”

“…As the current system of the simulation is more complicated than the earlier system (5CB + 10CB), the MD time of the equilibrium was first extended to lower the fluctuations of the mixture system ( Figure 1). The mean director vector data of the ensemble were used to calculate the mean squared displacement [10][11][12][13]. This technique made it easy to perform numerical analysis after obtaining the data from the MD simulation.…”

“…This technique made it easy to perform numerical analysis after obtaining the data from the MD simulation. The rotational viscosity equation was derived from two equations: the Einstein relation and the Stokes-Debye-Einstein equation [7,[10][11][12][13]. The essential factors of the rotational viscosity equation were the squared displacement of the mean director as a function of time and the mean volume and the mean temperature, which were obtained from the MD computer simulation.…”