A study on frustrated chiral liquid-crystal phases with large pitch distances by molecular simulations

It is well known that rod- or disk-like molecules may create various liquid crystal phases, which are observed between those of liquid and solid, under certain thermo-physical conditions. Many studies have been conducted to... [ view full abstract ]

It is well known that rod- or disk-like molecules may create various liquid crystal phases, which are observed between those of liquid and solid, under certain thermo-physical conditions. Many studies have been conducted to reveal the relationship between the molecular interactions and the macroscopic structures, however, predicting the self-assembled structure of molecules is still difficult, especially in the case of systems that involve topological defects and intrinsic frustration. For example, chiral liquid crystal phases originate from the frustration between molecular alignment and macroscopic chirality. Frustrated chiral phases are thermodynamically interesting, however, there are relatively a few studies focusing on the nature of their frustration and molecular-scale physics.

In this study, we investigated the effects of molecular interactions on self-assembly using a computer simulation approach. Molecular simulations using simple molecular models, such as the Gay-Berne model, give important insight to understand the phase behavior by observing the influence of potential parameters. However, there are two aspects that must be treated correctly in simulating such systems; one is the pitch distance, and the other is the periodic boundary condition. For these simulations, the systems with large pitch distances must be prepared to allow the formation of the helical structures that arise due to the molecular chirality. Three-dimensional periodic boundary conditions are often used in such simulations to represent a bulk state, but they sometimes induce serious artifacts due to inappropriate periodic images. In this study, therefore, the simulations with a large pitch distance were performed with hybrid planar anchoring in order to observe the phase behavior of chiral liquid-crystals systems.