Multi-paradigm modeling of dynamical crack propagation in silicon using the ReaxFF reactive force field

We report a study of dynamic cracking in a silicon single crystal in which the ReaxFF reactive force field is used for several thousand atoms near the crack tip while more than 100,000 atoms of the model system are described with a simple nonreactive force field. The ReaxFF is completely derived from quantum mechanical calculations of simple silicon systems without any empirical parameters. Our results reproduce experimental observations of fracture in silicon including differences in crack dynamics for loading in the [110] or [100] orientations and dynamical instabilities with increasing crack velocity. We also observe formation of secondary microcracks ahead of the moving mother crack.