Abstract
We employ Monte Carlo simulations in a specialized isothermal-isobaric and in the grand canonical ensemble to study structure formation in chiral liquid crystals as a function of molecular chirality. Our model potential consists of a simple Lennard-Jones potential, where the attractive contribution has been modified to represent the orientation dependence of the interaction between a pair of chiral liquid-crystal molecules. The liquid crystal is confined between a pair of planar and atomically smooth substrates onto which molecules are anchored in a hybrid fashion. Hybrid anchoring allows for the formation of helical structures in the direction perpendicular to the substrate plane without exposing the helix to spurious strains. At low chirality, we observe a cholesteric phase, which is transformed into a blue phase at higher chirality. More specifically, by studying the unit cell and the spatial arrangement of disclination lines, this blue phase can be established as blue phase II. If the distance between the confining substrates and molecular chirality are chosen properly, we see a third structure, which may be thought of as a hybrid, exhibiting mixed features of a cholesteric and a blue phase.
Highlights
Chirality is a symmetry property that is omnipresent, in many fields of science [1], and in everyday life
The latter authors observed novel disclination-line topologies in blue phase I under severe confinement conditions [25]. Almost all these previous theoretical studies have been based upon mesoscopic approaches, such as the Frank-Oseen elastic equations [26], whereas only a few studies to date employ molecular simulations, such as molecular dynamics or Monte Carlo (MC)
In the z-direction, where the solid substrates are separated by a fixed distance, sz, the implementation of hybrid anchoring [see Equation (10)] is advantageous in avoiding spurious stresses if the ratio of 2sz /p is non-integer, where p denotes the pitch length characterizing chiral structures forming in that direction
Summary
Chirality is a symmetry property that is omnipresent, in many fields of science [1], and in everyday life. A interesting class of materials often exhibiting chirality are liquid crystals It is the combined effect of molecular chirality and the formation of orientationally ordered, but positionally disordered, nematic or smectic mesophases, which gives rise to new structures, such as cholesteric or blue phases, to which the present article is devoted. The latter authors observed novel disclination-line topologies in blue phase I under severe confinement conditions [25] Almost all these previous theoretical studies have been based upon mesoscopic approaches, such as the Frank-Oseen elastic equations [26], whereas only a few studies to date employ molecular simulations, such as molecular dynamics or Monte Carlo (MC).
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