Three-dimensional fracture via large-scale molecular dynamics

A series of massively parallel molecular dynamics simulations with up to 35 million atoms is performed to investigate dislocation emission from a thre e-dimensional crack. We observe dislocation loops emitted from the crack fr ont, both in the bulk and near the free surfaces. The sequence of dislocati on emission in the process of crack blunting strongly depends on the crysta llographic orientation of the crack front and differs strikingly from anyth ing previously conjectured. This finding is essential to establish a precis e dislocation emission criterion (i.e: intrinsic ductility criterion). We a lso find that boundary conditions and interatomic force laws have a signifi cant effect on jogging or blunting dislocation emission modes. (C) 1998 Els evier Science Ltd. All rights reserved.