Domain walls in two-dimensional nematics confined in a small circular cavity

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de las Heras, Daniel ; Velasco, Enrique:
Domain walls in two-dimensional nematics confined in a small circular cavity.
In: Soft Matter. Bd. 10 (2014) Heft 11 . - S. 1758-1766.
ISSN 1744-6848
DOI: https://doi.org/10.1039/C3SM52650J

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Abstract

Using Monte Carlo simulation, we study a fluid of two-dimensional hard rods inside a small circular cavity bounded by a hard wall, from the dilute regime to the high-density, layering regime. Both planar and homeotropic anchoring of the nematic director can be induced at the walls through a free-energy penalty. The circular geometry creates frustration in the nematic phase and a polar-symmetry configuration with a distorted director field plus two +1/2 disclinations is created. At higher densities, a quasi-uniform structure is observed with a (minimal) director distortion which is relaxed via the formation of orientational domain walls. This novel structure is not predicted by elasticity theory and is similar to the step-like structures observed in three-dimensional hybrid slit pores. We speculate that the formation of domain walls is a general mechanism to relax elastic stresses under the conditions of strong surface anchoring and severe spatial confinement.