Helical structures of achiral liquid crystals under cylindrical confinement

Confined liquid crystals (LCs) exhibit complex and intriguing structures, which are fascinating fundamental problems in soft matter. The helical structure of cylindrical cavities is of great importance in LC studies, particularly for their application in optical devices. In this study, we employ molecular dynamics simulations to explore the behavior of achiral smectic-B LCs confined in narrow cylindrical cavities, where geometric frustration plays an important role. By increasing the cylinder size, LCs exhibit a transition from multi-helical to layered structures. Notably, we observe two stable structures, namely the helical structure and the layered structure, at moderate cylinder size. We also investigate the effects of the arrangement of cylindrical wall particles (hexagonal or square array) and anchoring strength on the LC structure. Our findings reveal that both the hexagonal array and strong anchoring strength promote the formation of helical structures. Our study provides novel insights into the confinement physics of LCs and highlights the potential for achieving helical structures in achiral LCs, which will expand the future applications of LCs.