Reactive molecular dynamics simulation of thermal decomposition for nano-FOX-7

1,1-Diamino-2,2-dinitroethylene (FOX-7) is well-known as one high-energy insensitive material. The size effect of the nano-crystal on the pyrolysis are extremely important for ignition and reaction pathways under extreme conditions. The thermal decomposition of nano-FOX-7 was investigated utilizing molecular dynamics method with reactive force field. The pyrolysis simulation showed that the potential barrier of nano-FOX-7 at 3000 K are higher than that at 2000 K. The temperature distribution of nano-FOX-7 in the temperature-rise periods shows that the decomposition occurs first at the central part of the crystal. Based on the analysis of chemical species, three types of initial reaction pathways were identified, among which the fission of the C–NH₂ bond may be a new reaction pathway. A decomposition network from initial reactant to the main products was proposed to provide insights into the decomposition mechanism on atomic level. The mass distribution of products showed that the clusters among the decomposition products can inhibit the violent reaction to a certain extent. In addition, the analysis of the nano-crystal effect on the FOX-7 decay shows that the numbers of N₂ and CO₂ are related to the nanoparticle size. Graphical abstract: [Figure not available: see fulltext.]