Thermal decomposition mechanism of TKX-50 explored by neural network based molecular dynamics simulation

XH Wang and JQ Yang and GZ Hao and YB Hu and XJ Feng and W Jiang, FUEL, 397, 135420 (2025).

DOI: 10.1016/j.fuel.2025.135420

Dihydroxylammonium 5, 5 '-bistetrazole-1, 1 '-diolate (TKX-50) is an energetic crystal composed of hydroxylammonium cations and bistetrazole anions, whose decomposition process involves complex chemical reactions and produces a wide variety of molecular species. In this study, a quantum chemistry-level neural network potential (NNP) was developed to simulate the thermal decomposition of TKX-50. Throughout the simulation, we tracked the evolution of key products and proposed a detailed decomposition mechanism. The results show that the hydroxylammonium cations decompose via three initial pathways: N-H bond cleavage, O-H bond cleavage, and N-OH bond cleavage, occurring in a 4:1:1 ratio. The tetrazole ring primarily accepts the proton dissociated from the hydroxylammonium cation at either the O1 or N4 position. Proton transfer to the N4 position facilitates the cleavage of the tetrazole ring, leading to the release of N2, while proton transfer to the O1 position promotes the dissociation of the OH group. Four decomposition pathways (P1-P4) of the tetrazole ring were identified, with the branching ratio following the order P1 > P2 >> P3 approximate to P4. Furthermore, we propose a general mechanism for the conversion of N-O gas products to N2 during the decomposition of energetic materials.

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