Nematic ordering and defects on the surface of elongated capsule-shaped nano-particles.

Abstract

We examine the ordering of hard rods confined to the surface of elongated nano-particles or capsules using grand canonical computer simulations. The nano-particles consist of a cylindrical section of length L_C and diameter D_C and two hemispherical end-caps of diameter D_C. Due to the orientational symmetry of the nematic phase, the director configuration cannot uniformly cover the surface and we observe four s = +½ defects on the surface of the nano-particle. These defects are found to be located, on average, at the ends of the cylindrical section of the nano-particle around the circumference of the hemispherical end-caps. Two defects occur at each end, and these repel such that they are on opposite sides of the nano-particle. However, the locations of the defects at opposite ends of the nano-particle appear to be uncorrelated. This behaviour appears to be independent of the length of the nano-particle for all but the shortest elongations.