Initial reaction pathways of anhydrous hydrazine deflagration: insights from Ab initio molecular dynamics and coupled stimuli experiments

Understanding the microscopic mechanisms of anhydrous hydrazine (N 2 H 4 ) is critical for preventing cascading accidents. In order to elucidate the thermal decomposition behavior and deflagration hazards, we carried out slow cook-off tests on gram-scale samples, impact sensitivity evaluations at varying temperatures, and ab initio molecular dynamics (AIMD) simulations. Results indicate that a distinct evaporation plateau (∼1.4 h at 117.1 o C) occurs in glass containers. Conversely, no plateau is detected in stainless steel, suggesting that high thermal conductivity masks pre-runaway evaporation. The dominant impact hazard mechanism is identified not as intrinsic decomposition, but as an impact-induced, temperature-sensitized N 2 H4-O 2 deflagration. High-speed imaging supports this pathway, which is driven by aerodynamic dispersion and fuel-air mixing. Furthermore, AIMD simulations reveal the atomic-level signature of deflagration: an ultrafast (