Grain Boundary Buckling and Spin Glass Models

A systematic investigation is presented of grain boundaries and grain boundary networks in two dimensional flexible membranes with crystalline order. An isolated grain boundary undergoes a buckling transition at a critical value of the elastic constants, but, contrary to previous findings, the shape of the buckled membrane is shown to be asymptotically flat. This is in general not true in the case of a network of intersecting grain boundaries, where each intersection behaves as the source of a long range stress field. Unlike the case of isolated dislocations or disclinations, the energy associated with these stresses is finite; they can, however, destabilize the flat phase. The buckled phase can be modeled by an Ising spin-glass with long range antiferromagnetic interactions. These findings may be relevant to the understanding of the wrinkling transition in partially polymerized vesicles reported in recent experiments.