Analysis of Chemical Reaction Process after Pentaerythritol Tetranitrate Hot Spot Ignition

In this paper, ReaxFF force field combined with molecular dynamics method was used to study the ignition, deflagration, and detonation of pentaerythritol tetranitrate (PETN) induced by hot spots. The hot spot is 5.6% of the total volume. When the hot spot temperature is 1000 K, the deflagration and detonation of PETN cannot be observed in the simulation time of 200 ps. When the hot spot temperature is 2000 K, it corresponds to the heating time of 20 to 50 ps, deflation and detonation were observed. During hot spot ignition, the products of decomposition of the condensed phase PETN are dominated by NO₂ and HONO. The energy required for the C-C bond and C-ONO₂ bond cleavage in PETN is high, resulting in only a small amount of CH₂O and NO₃ during the reaction. Small nitrogen-containing molecules (such as NO₂, NO₃, HONO, HNO₃, etc.) mainly exist during thermal equilibrium, while the number of N₂ increases sharply during the thermal runaway stage, and a small amount of NH₃ and NH₂ are also produced. H₂O molecules are formed before CO₂ and N₂ are produced, and the number always dominates. During the thermal runaway, the entire system can maintain a spontaneous reaction, resulting in a sharp rise in temperature of about 2500 K in 20 ps. During this phase, the catalytic effect of H₂O accelerates the formation of CO₂ and N₂ due to the near Chapman-Jouguet point in the crystal. PETN is a weak oxygen balance explosive that results in a small amount of CO and H₂ production during the thermal instability phase. When the reaction is balanced, the relative molecular mass is close to or exceeds that of PETN. The product is only less than 1% of the total mass fraction, while the small molecule product is as high as 78%, and some relative molecular masses are [75,225]. The intermediates account for about 21%. Rapid and complex reaction events make it difficult to accurately predict the structure of these intermediates by existing experiments and calculations, which will be the focus of future research.