(360at) Explosive Mechanochemistry: Foundations for Strength-Aware Chemical Kinetics

Molecular dynamics shows strong synergy between high-rate strength behavior and chemistry in explosives, with plastic deformation localizing heat into hot spots and reducing reaction barriers through mechanochemistry. Nanoscale shear bands form dynamically in many shocked explosives, and we show that these regions are 200 times more reactive than bulk crystal in TATB (1,3,5-triamino-2,4,6-trinitrobenzene). Enhanced reactivity is traced to molecular deformations that are identified based on intramolecular strain energy. Axial compression simulations show that substantial molecular deformations are generated for all crystal orientations at pressures greater than 10 GPa, which qualitatively explains unusual changes in TATB reactivity with increasing shock pressure. Despite fine-scale complexity, the global stress-strain response is straightforward with a flow stress that scales with the shear modulus. This suggests a plausible route to simplify treatments of strength, which when coupled to our measured intramolecular strain energy distributions, provides grounds for parameterizing a “strength-aware” chemical kinetics model for TATB-based explosives.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Approved for unlimited release, LLNL-ABS-828054.