Nematic and Smectic Phases: Dynamics and Phase Transition

Aurélien Bailly-Reyre,Hung T Diep

doi:10.3390/sym12091574

Abstract

We study in this paper the dynamics of molecules leading to the formation of nematic and smectic phases using a mobile 6-state Potts spin model with Monte Carlo simulation. Each Potts state represents a molecular orientation. We show that, with the choice of an appropriate microscopic Hamiltonian describing the interaction between individual molecules modeled by 6-state Potts spins, we obtain the structure of the smectic phase by cooling the molecules from the isotropic phase to low temperatures: molecules are ordered in independent equidistant layers. The isotropic-smectic phase transition is found to have a first-order character. The nematic phase is also obtained with the choice of another microscopic Hamiltonian. The isotropic-nematic phase transition is a second-order one. The real-time dynamics of the molecules leading to the liquid-crystal ordering in each case is shown by a video.

Highlights

Nematic and smectic phases have been the subject of intensive investigations since the discovery of liquid crystals (LC) [1,2]
We will first describe the model for the smectic case in Section 2 and we show the results obtained by Monte Carlo (MC) simulations
A video showing the dynamics of the formation of the smectic phase is available at the link given in Ref. [29]

Summary

Introduction

Nematic and smectic phases have been the subject of intensive investigations since the discovery of liquid crystals (LC) [1,2]. LC are generated by strong structural anisotropy objects. The way these constituents are arranged to form LC depends usually on the temperature, but, for some mesomorphic phases, it can be a function of the concentration of the molecules in a solvent. We know that the nematic phase is the closest phase to the liquid phase and the most common It has no long-range positional order but a global orientational order. As for the smectic phase, it is the phase which looks like the most to a crystalline solid and for which molecules are ordered in equidistant layers It shows a long-range positional order (at least in one direction) and an orientational order in each layer

Methods

Results

Conclusion