Quasicontinuum models of fracture and plasticity

The development of modeling tools which allow for the simultaneous treatment of scales ranging from Ångstroms to microns has stood out as one of the main challenges in materials modeling. In this paper we discuss a formulation of the quasicontinuum (QC) method that allows for a treatment of internal interfaces, opening the possibility of simulating the interactions of cracks, dislocations and grain boundaries. The model is applied to crack tip deformation and is shown to account for both brittle fracture and crack tip dislocation emission. A key example of the method is the treatment of a crack propagating into a grain boundary which reveals both migration of the boundary and that the boundary is a source for the emission of dislocations.