Reaction Kinetics Properties of 1,3,5-Triamino-2,4,6-Trinitro-benzene: A DFTB Study for Thermal Decomposition

The thermal decomposition of 1,3,5-Triamino-2,4,6-Trinitrobenzene (TATB) is studied using quantum-based molecular dynamics (MD) method at several temperatures, to uncover its fundamental reaction mechanism and kinetics properties. The primary decomposition pathways, key intermediate products and their population evolutions are systematically investigated. We uncover four sequential reaction stages during TATB thermal dissociation for the first time: (1) C-NO2 bond cleavage and amino dehydrogenation; (2) hydrogen transfer to nitro or NO2, further converting into NO and H2O; (3) carbon oxidation and molecular ring deep fission to generate CO and small -CN fragments; (4) formation of final gaseous N2 and CO2. The fission or formation rate constants and reaction energy barriers of the main chemical bonds are obtained by exploring the kinetics process. We confirm that C-NH2 bond breaking is the rate-controlled step for carbon oxidation, while N-N bond formation is the rate-controlled step for N2 generation. Besides, we also get the global exothermic reaction rate and reaction heat based on analysing the change of potential energy. All the results not only give a deep insight for the chemical performance of TATB, but also can serve as prerequisite parameters to improve the macroscopic physical models for explosive reactivity.