Unraveling the temporal evolution and kinetics characteristics of crucial products in β-HMX thermal decomposition via ReaxFF-MD simulations

ZH He and GF Ji, NEW JOURNAL OF CHEMISTRY, 49, 14351-14360 (2025).

DOI: 10.1039/d5nj02124c

The temporal evolution of crucial products and their kinetic features is important for understanding the reaction behaviors of high-explosive pyrolysis. We perform the large-scale and long-duration reactive force field molecular dynamics simulations to unravel the intricate reaction characteristics of beta-HMX thermal decomposition across 1250-2500 K. The temperature-dependent reaction pathways and kinetic features of gaseous products, intermediates, and carbon clusters are systematically investigated. The results demonstrate that the initial reaction mechanism shifts from N-O cleavage to N-NO2 homolysis at elevated temperatures, which increases the energy barrier for N2 formation from 9.02 to 27.93 kcal mol-1, attributed to the depletion of the original N-N coordination precursor. H2O is consumed at high temperatures, corresponding to the enhanced CO2 and H2 production through water-gas shift-like reactions. Intermediate nitrogen oxides (NO2, NO3, and NO) exhibit rapid formation-consumption cycles, while their hydrogenated derivatives (NO2H, NO3H, and NOH) display higher stability with higher dissociation energy barriers. Carbon clusters evolve from nitrogen-rich C3N3 heterocycles below 1750 K to C/O-dominated quasi-planar structures above 2000 K. These insights into intermediate dynamics, competing reaction pathways, and carbon cluster evolution will establish a theoretical foundation for developing combustion product equations of state, advancing the performance prediction of high explosives.

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