Substituents effect on the heat-induced pyrolysis mechanism of energetic materials: A Case of Reactive Molecular Dynamics Simulations on Nitrobenzene Compounds

Abstract

The initial decomposition reactions of 1,3,5-trinitrobenzene (TNB), picric acid (PA), 2,4,6-trinitrotoluene (TNT), 2,4,6-trinitroaniline (TNA) and 2,4,6-trinitrophenylmethylnitramine (Tetryl) were studied using ReaxFF-lg molecular dynamics simulations, and the substituents effect on the thermal decomposition behaviours of nitrobenzene compounds was evaluated through the reactant number, initial decomposition pathway, products and cluster analysis. Results showed that the introduction of substituents could promote the decomposition of reactants, increase the frequency of nitro-nitrito isomerization reaction and intermolecular H or O atom transfer reaction, and reduce the frequency of direct nitro dissociation reaction. Notably, these effects were most obvious in the case of TNT. Owing to the introduction of substituents, the number of hydrogen-containing products (HO2N, H2, H2O and NH3) increased. Different functional groups can also lead to variations in the quantities of decomposition products and clusters distribution. The decomposition process of the five nitrobenzenes were detailed examined through the analysis of intermediate products, revealing the distinct influence of the substituent groups. These findings contribute to an enhanced understanding of how different substituent groups influence the energy release mechanisms of energetic compounds.