Theory and simulation of freeze-fracture in cholesteric liquid crystals.

Cholesteric and nematic liquid crystals can be quick-frozen to form a glass with long-range order of molecular orientation. The glass retains the varying director orientation of the original liquid crystal phase. In order to interpret electron micrographs of fractured surfaces on such samples we have developed a simple theory of fracture in spatially varying anisotropic materials. In this theory the expression for energy per unit area released by crack formation is gamma (proportional to) square root [n (.)( 1 + bQ(1))(.)n], where Q(1) is the traceless Landau tensor for unit order parameter and n is a unit vector normal to the crack surface. The constant b is a function of the ratio of length to width of the average volume occupied by each molecule. The crack front is constrained to an advancing plane that is parallel to the stress and to the initial front.