The development of modeling tools which allow for the simultaneous treatment of scales ranging from Angstroms 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.
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We are grateful to C. Briant, R. Clifton, B. Freund and D. Rodney for discussions, to S. W. Sloan for use of his Delaunay triangulation code and to M. Daw and S. Foiles for the use of their Dynamo code. We are also grateful to AFOSR who supported this work under grant number F49620-95-I-0264 and the NSF through grants CMS-9414648 and the Brown MRSEC DMR-9632524, and the DOE through grant DE-FG02-95ER14561. RM thanks the NSERC for support.