Biaxial nematics of hard cuboids in an external field

Abstract

By computer simulation, we model the phase behaviour of colloidal suspensions of board-like particles under the effect of an external field and assess the still disputed occurrence of the biaxial nematic (N_B) liquid crystal phase. The external field promotes the rearrangement of the initial isotropic (I) or uniaxial nematic (N_U) phase and the formation of the N_B phase. In particular, very weak field strengths are sufficient to spark a direct I–N_B or N_U–N_B phase transition at the self-dual shape, where prolate and oblate particle geometries fuse into one. By contrast, forming the N_B phase at any other geometry requires stronger fields and thus reduces the energy efficiency of the phase transformation. Our simulation results show that self-dual shaped board-like particles with moderate anisotropy are able to form N_B liquid crystals under the effect of a surprisingly weak external stimulus and suggest a path to exploit low-energy uniaxial-to-biaxial order switching.