Impact-induced hotspot formation and sensitivity descriptor in energetic crystals revealed by deep potential...

Understanding the microscopic origin of impact sensitivity (IS) in energetic materials (EMs) requires a physically meaningful descriptor that links molecular-scale dynamic response to macroscopic behavior. In this work, molecular dynamics simulations based on a Deep potential (DeepMD) were employed to investigate the impact response of α-RDX nanocrystals under practical drop-weight-like loading conditions. An explicit atomic impactor was introduced to capture heterogeneous mechanical responses, including stress concentration, energy localization, and compression-shear coupled deformation. The simulations reveal that impact-induced reaction initiation proceeds through a sequence of impact energy deposition, mechanical compression, hotspot formation, and rapid decomposition. These processes collectively reflect the intrinsic resistance of material to impact-induced failure at the molecular scale. The decomposition fraction is used as an observable to identify the onset of irreversible reactions, from which the critical impact velocity (v_c) is defined. v_c serves as a molecular-level descriptor of impact sensitivity that quantifies the material resistance to impact-induced failure, providing a physically interpretable measure of impact resistance. Comparative simulations on eight energetic crystals (IS = 3.5-120 J) reproduce the experimental impact sensitivity ranking with a good correlation (R² = 0.91) between the descriptor v_c² and IS. These results establish a direct link between atomistic failure processes and macroscopic impact sensitivity, providing a descriptor-based framework for the quantitative prediction and virtual screening of EMs with improved safety-performance balance.