Self-Similarity and the Importance of 3D Effects in the Formation of Explosive Hot Spots

Shock-induced collapse of voids with diameters in the 100-1000 nm range is thought to govern explosive initiation, but details of the hot spot formation process at this scale remain elusive to "full-physics" treatments based in all-atom molecular dynamics (MD). Using large-scale quasi-2D MD simulations, we predict the features of hot spots formed in a crystalline molecular explosive on multi-micron computational domains. Comparing a range of pore diameters and shock loading orientations shows a high degree of consistency in the hot spots formed at a given shock strength. A statistical test is developed that reveals rapid convergence and self-similarity in the predicted hot spot temperature fields for a given shock condition. Billion-atom scale MD simulations of hot spot formation with 3D spherical voids give direct evidence that widely adopted (quasi‑)2D approximations significantly underestimate peak hot spot temperatures and reaction rates at shock initiation conditions. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-855729.