Minimal surfaces, screw dislocations, and twist grain boundaries

Large twist-angle grain boundaries in layered structures are often described by Sehrk's first surface, whereas small twist-angle grain boundaries are usually described in terms of an array of screw dislocations. We show that there is no essential distinction between these two descriptions and that, in particular, their comparative energetics depends crucially on the con structure of their screw-dislocation topological defects. [S0031-9007(99)08846-8].