A coarse-grain reactive model of RDX: molecular resolution at the μm scale

Predictive models for the thermal, chemical, and mechanical response of high explosives (HEs) at extreme conditions are important for investigating their performance and safety. We introduce a particle-based, reactive model of 1,3,5-trinitro-1,3,5-triazinane (RDX) with molecular resolution utilizing generalized energy-conserving dissipative particle dynamics with reactions (GenDPDE-RX). The model is parameterized from all-atom reactive molecular dynamics (MD) simulations, thus bridging atomic processes to the mesoscales, including microstructure and defects. It accurately captures the response of RDX under a range of thermal and shock loading observed in atomistic simulations. In addition, the model also correctly portrays the interplay of shock and microstructure in hotspot formation and transition to deflagration. Exploiting the model's high computational efficiency, we investigate mesoscale systems involving millions of molecules and characterize size-dependent criticality of hotspots in RDX. The combination of accuracy and computational efficiency of our reactive model provides a tool for investigation of mesoscale phenomena, such as the role of microstructure and defects in the shock-to-deflagration transition, through particle-based simulation.