A Hotspot’s Better Half: A Characterization of the Local Potential Energy Rise in Mechanically Induced Hotspots

Shock loading of high explosives leads to energy localization into hotspots, which are thought to govern the initiation of detonation. Hotspots are typically characterized in terms of their size and temperature. Criticality of a hotspot depends on a competition between thermal diffusivity and endothermic reactions that tend to quench the hotspot against exothermic reactions that can transform the hotspot into a deflagration wave. However, this view ignores the role of potential energy (PE) as a descriptor of energy localization and criticality. We show through large-scale molecular dynamics simulations of TATB pore collapse that more energy is localized in PE than in kinetic energy (KE). Furthermore, the spatial extent and diffusivity of the PE and KE hotspots are significantly different, and far from expectations based on equipartition. An analysis of the MD trajectories reveals the molecular origin of this puzzling observation. Prepared by LLNL under Contract DE-AC52-07NA27344. Approved for unlimited release, LLNL-ABS-794457.