Shock to Deflagration Transition of RDX: Role of Microstructure Investigated Through Mesoscale Reactive Model.

Predictive models for the thermal, chemical, and mechanical properties of high explosives (HEs) at extreme conditions are highly desirable to understand 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 the generalized energy-conserving dissipative particle dynamics with chemical reactions (GenDPDE-RX) method. The model is parameterized from all-atom reactive molecular dynamics simulations, thus, it bridges atomic processes to the mesoscale. We address shortcomings of current state-of-the-art mesoscopic models in reproducing the response of RDX under a range of thermal and shock loading. In addition, the model also correctly portrays the interplay of shock and microstructure in hotspot formation and transition to deflagration. We attribute the vast improvement in accuracy to two distinguishing features: incorporation of a reduced-order chemistry model and a top-down parametrization approach. Exploiting the model’s high computational efficiency, we investigate microscale systems and validate them by investigating size-dependent criticality of RDX hotspots that has been predicted with continuum models.