Carbon-rich foam formation in the early stages of detonation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)

Abstract

The detonation of carbon-rich high explosives yields small molecules and an excess of carbon, which forms carbon nanoparticles in post-detonation recovery experiments. The formation mechanism of these nanoparticles has been concealed experimentally by the opacity of the reaction zone and numerically by the length and time scales involved in this process. Consequently, prior to nanoparticles, the atomic-scale chemistry by which the carbon atoms of the detonating system transform into excess carbon remains unclear. To address this issue, representative sizes of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) samples were considered at densities around the von Neumann spike or around the Chapman–Jouguet state, two characteristic points of the Zel’dovich–von Neumann–Döring detonation model. The adiabatic, constant-volume decomposition of these TATB samples and their chemical evolution were studied by means of Reactive Molecular Dynamics (RMD). The RMD simulations show the formation of a carbon- and oxygen-rich foam mixed with a fluid phase of small molecules. The growth of pure carbon structures within the foam exhibits two regimes: first, the quick growth of medium-sized carbon units, followed by their slow coalescence through interconnection, which requires structural rearrangements. Depending on the thermodynamic conditions, the connected carbon units can form an extended network of pure carbon that eventually percolates beyond the simulation domain. After 50+ ns, the foam does not evolve much, likely maintained out of chemical equilibrium as the extended carbon network remains far from the structure of compact nanoparticles.