Intergranular Hotspots: A Molecular Dynamics Study on the Influence of Compressive and Shear Work

BW Hamilton and MP Kroonblawd and J Macatangay and HK Springer and A Strachan, JOURNAL OF PHYSICAL CHEMISTRY C, 127, 9858-9870 (2023).

DOI: 10.1021/acs.jpcc.3c01197

Numerous crystal- and microstructural-level mechanismsare at playin the formation of hotspots, which are known to govern high explosivesinitiation behavior. Most of these mechanisms, including pore collapse,interfacial friction, and shear banding, involve both compressiveand shear work done within the material and have thus far remaineddifficult to separate. We assess hotspots formed at shocked crystal-crystalinterfaces using quasi-1D molecular dynamics simulations that isolateeffects due to compression and shear. Two high explosive materialsare considered (TATB and PETN) that exhibit distinctly different levelsof molecular conformational flexibility and crystal packing anisotropy.Temperature and intramolecular strain energy localization in the hotspotare assessed through parametric variation of the crystal orientationand two velocity components that respectively modulate compressionand shear work. The resulting hotspots are found to be highly localizedto a region within 5-20 nm of the crystal-crystal interface.Compressive work plays a considerably larger role in localizing temperatureand intramolecular strain energy for both materials and all crystalorientations considered. Shear induces a moderate increase in energylocalization relative to unsheared cases only for relatively weakcompressive shock pressures of approximately 10 GPa. These resultshelp isolate and rank the relative importance of hotspot generationmechanisms and are anticipated to guide the treatment of crystal-crystalinterfaces in coarse-grained models of polycrystalline high-explosivematerials.

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