MOLECULAR DYNAMICS SIMULATIONS OF DETONATION IN DEFECTIVE EXPLOSIVE CRYSTALS

Large-scale molecular dynamics simulations using a REBO (reactive empirical bond-order) model potential have been performed in order to investigate the detonation process in condensed phase explosives at a microscopic scale. Starting from a diatomic AB molecular crystal, shock initiation of the exothermic chemical reaction 2AB → A2 + B2 can lead to a steady detonation wave for sufficiently strong shock impacts. Perfect crystals are remarkably insensitive, requiring shock compressions of 25 % (nearly 100 kbar) before delayed (ho-mogeneous) initiation occurs in the shock-compressed (and heated) AB liquid. Point defects, such as vacancies or iso-lated A · or B · radical atoms, have no observable effect on this threshold, except in some cases to cause a few localized reac-tions that fail to propagate. On the other hand, extended structural defects can be quite effective at lowering the deto-nation threshold by providing heterogeneous initiation sites (hot spots). We report studies of void collapse in two-dimensional AB solids, focusing on the effect of void geome-try (circular vs. elliptical) and size