Manipulation of Liquid Crystals by an Orienting Force in MD Simulations

Abstract

We have developed a simple yet powerful method to allow the manipulation of liquid crystal molecules in molecular dynamics simulations with an orienting force. We describe this method and demonstrate its use with simulations of 2-(4-octyloxyphenyl)-5-octyloxypyrimidine to transform an isotropic initial configuration into either nematic or smectic configurations. We also extend the method by limiting the orienting force to a small volume of the system in order to mimic the presence of a pinning surface in a real device. The method we describe could easily be extended to any similar mesogen.

Algorithms forGPU‐based molecular dynamics simulations of complex fluids: Applications to water, mixtures, and liquid crystals

“…The 80/20 mixture of n ‐hexane and 2‐propanol has a total density of 0.660 g cm − and a temperature of 298 K. Benchmarking tests for the 2PhP liquid crystal are conducted at a density of 0.9 g cm − and a temperature of 350 K. The generation of distribution functions, illustrative snapshots, and energies requires a careful and lengthy equilibration to yield well‐defined layers. Following Yan and Earl [8] and Daub and Cann, we start with an initial temperature of 600 K and apply an ordering field. After simulating for 0.25 ns, the temperature is gradually lowered to 350 K, over 0.25 ns, while the strength of the ordering field decreasing with temperature.…”

“…The introduction of the third GPU only marginally impacts the performance for the smaller system but a 0.047 ns day 21 performance is expected for 8192 mesogens. These simulation times make it possible to examine systems that are much larger than before [36,42] and to simulate for longer times. For example, a 1:1:16 simulation cell of 8192 2PhP molecules would result in the cell with a long side of roughly 1000 Å .…”