Decomposition Mechanisms of α-Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine Nanoparticles at High Temperatures

Abstract

Density functional tight-binding molecular dynamics simulations with dispersion corrections were performed to study the adiabatic initial decomposition processes of molecular explosive α-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (α-HMX) nanoparticles (NPs) with the diameters of 1.4–2.8 nm at high temperatures from 2400 to 3000 K. The results indicate that the global thermal decompositions of the HMX NPs present great dependence on the temperature and particle size. The initial decomposition process of the HMX NPs includes two sequential stages: (i) competition between rapid expansion and unimolecular decompositions at surfaces; (ii) subsequent complex uni- and bimolecular decompositions. The main decomposition pathway at low temperatures is the isomerization reaction of the HMX molecule, which is quite different from the N–NO2 homolysis with ring opening at high temperatures. A second-order rate model was established to rationalize the global decompositions of the HMX NPs at different temperatures ...