An All-atom Molecular Dynamics Simulation Study Of Liquid Crystal Cell

With the rapid development of economy, the application of liquid crystal has gotdeeply into all aspects of people’s life and the requirement on the properties of liquid crystaldisplay (LCD) is getting higher and higher. Therefore, a deeper research on the propertiesof liquid crystal materials becomes necessary. However, due to the limitation ofexperimental conditions, the microscopic study of liquid crystal on the molecular level stillfaces great difficulties. There is an urgent demand for new theory and research method.Application of computer brings about possibilities of saving research cost, improvingefficiency and predicting new material properties by using molecular dynamics simulationon liquid crystal systems. Using this method, the microscopic aspects of liquid crystalsystems can be observed and analyzed on the molecular level and the macroscopicproperties of the liquid crystal systems can be obtained through statistics. In this paper weinvestigate the response behavior of liquid crystal cell using molecular dynamics simulation.The material is5CB liquid crystal in nematic phase. The seven handred and twenty5CBmolecules are filled in actual density between two parallel substrates made of monolayercarbon plates to form a liquid crystal cell. The size of the cell is5.861×11.9×4.23nm3. Thesimulation temperature is300K. We add different voltages between two substrates andperform molecular dynamics simulation for the liquid crystal cell, and then analyze theorientation of liquid crystal molecules under voltage. Through statistics we obtain theorientation curves of the directors of each liquid crystal layer with the number of layersunder different voltages and the curve of the maximum decline angle of the middle layerwith voltage. These curves are in good consistence with experimental results, indicatingthat our microscopic model for liquid crystal cell is really reasonable. Since the model is anall-atom model, various details of the liquid crystal response under voltage are contained inthe simulation trajectories. This provides a firm basis for deeper and more detailedinvestigation on the properties of liquid crystal materials.