Revisiting hotspot ignition and growth due to pore collapse and shear localization using atomistics-consistent material models

The calculation of hotspot ignition and growth rates is crucial to providing closure in the form of burn models to hydrocodes that predict the shock-to-detonation transition in energetic materials. Previous attempts at meso-scale calculations of energy localization to form reactive hotspots have relied on material models, including thermophysical and material strength properties, which did not adequately represent several aspects of the material behavior. Here, we revisit the calculations of reactive hotspot evolution, utilizing recently developed atomistic-consistent material models for the energetic crystal HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane). These updated physical models lead to significant differences in hotspot development at pore collapse sites by capturing energy localization in shear bands. In light of the distinctively different physics of shock-induced localization in the atomistics-consistent models, we also reevaluate the approach to calculate hotspot ignition and growth. These new meso-scale quantifications of energy localization rates are compared with previous approaches and the resulting differences are highlighted. The present work advances both physical understanding and quantification of the hotspot ignition and growth rates in HMX, informing the development of improved meso-informed reactive burn models for the prediction of sensitivity of such materials.