Three-dimensional pore collapse in shocked energetic crystals: Evaluating atomistics-consistent continuum models against molecular dynamics

The shock-induced collapse of three-dimensional (3D) pores in the energetic crystal RDX (1,3,5-trinitro-1,3,5-triazinane) is investigated using all-atom molecular dynamics (MD) and continuum simulations employing atomistics-consistent material models. We systematically investigate pore-collapse behavior by varying shock strengths and pore geometries, including spherical and ellipsoidal configurations. Transitions between strength (plasticity)-dominated and hydrodynamic collapse regimes are delineated, as well as the influence of pore orientation and length scale (nm to μm) on energy localization. By bridging atomistic and continuum descriptions, the study examines the role of three-dimensionality in hotspot formation and evaluates the accuracy of continuum predictions against MD benchmarks for inert pore collapse in RDX. We also evaluate atomistics-consistent material models for RDX, identifying aspects of pore collapse and hotspot formation that align with or deviate from MD. Differences between 3D and 2D pore collapse and hotspots are elucidated and aspects such as effects of crystalline anisotropy, orientation of elongated ellipsoidal pores, and pore size are assessed. This work points to avenues for further improvement of meso-scale models for predicting detonation initiation in RDX-based energetic materials in microstructure-aware multiscale frameworks.