Pyrolysis of CL20-TNT cocrystal from ReaxFF/lg reactive molecular dynamics simulations

ReaxFF/lg reactive force field is the extention of ReaxFF by adding a van derWaals attraction term. It can be used to well describe density and structure of crystal, moreover, the macroscopic property of detonation is significantly influenced by the density of energetic material. We report on the initial thermal decomposition of condensed phase CL20-TNT cocrystal under high temperature here. The time evolution curve of the potential energy can be described reasonably well by a single exponential function from which we obtain the initial equilibration and induction time, overall characteristic time of pyrolysis. Afterward, we also obtain the activation energy E_a (185.052 kJ/mol) from these simulations. All the CL20 molecules are completed before TNT decomposition in our simulations. And as the temperature rises, the TNT decomposition rate is significantly accelerated. The higher the temperature at which complete decomposition occurs, the closer to each other the times needed for CL20 and TNT to be completely decomposed will be. Product identification analysis with the limited time steps shows that the main products are NO₂, NO, CO₂, N₂, H₂O, HON, HNO₃. C?NO₂ and N?NO₂ bond homolysis jointly contribute to the results of the NO₂. The NO₂ yield rapid increases to the peak and then decreases subsequently. This process is accompanied with NO₂ participating in other reactions so that the N atom of NO₂ enters into the other N-containing molecule. Secondary products are mainly CO, N₂O, N₂O₅, CHO. N₂O has a strong oxidation ability, so that the distribution has a dramatic fluctuation characteristics.