Twist walls in nematic liquid crystals

Abstract

An approximate solution is derived for the structure of a twist wall between two regions of opposite 180° twist in a nematic liquid crystal film. The result is used to show that a twist wall is unstable unless the elastic constants of the nematic are such that K₂₂≤ ½(K₁₁ + K₃₃). Thus the observation of such walls in nematic liquid crystals is evidence of this elastic anisotropy. Experimental evidence is given for the validity of the approximate solution obtained.