Mechanisms and Kinetics of Thermal Decomposition of CL-20

In contrast to past studies of thermal decomposition mechanisms of explosives designed to determine the detailed chemical pathways by which these large organic molecules are transformed into small reaction products (N2, NO, N2O, HCN, CO, CO2, H2O, etc.)—crucial to predicting long-term stability for storage; sensitivity to heat and mechanical impact; and risk assessment associated with their usage, the purposes of this study were to investigate the initial chain of chemical events during CL-20 decomposition of isolated and condensed phases and, additionally, to analyze the nature, energetic, and kinetic patterns of the primary and secondary products. To improve atomistic understanding of the thermal decomposition of solid phase CL-20, (a high-energy nitramine explosive possessing R2N-NO2 functional groups) we performed a series of ab initio molecular dynamics simulations, finding that during unimolecular decomposition, unlike other nitramines, CL-20 has only one distinct initial reaction channel—homolysis of the N–NO2 bond. No HONO elimination reaction was observed during unimolecular decomposition; the ring breaking reaction was followed by NO2 fission.