The MD trajectories using the NNP are further analyzed by ReacNetGenerator to reveal the complex reaction network. The primary reaction pathways of RDX decomposition and the formation of final products are constructed in Fig. , where the arrow width represents the observed number of reactions. The major channel of RDX decomposition starts with N-N homolysis to produce NO2 molecules and RDR radicals, which agree with previous DFT studies . Then, the RDR radicals mainly decompose through three pathways: In our simulations using the NNP, the N-N homolysis is more critical compared to the ring-opening reactions and the H abstraction/addition reactions in the RDR decomposition as the corresponding frequency number is 49, 16 and 11. This finding here disagrees with the DFT calculations by Chakraborty et al. ; they reported that the RDR prefers to decompose through the ring-opening reactions rather than N-N homolysis. The reason might be attributed to the effects of neighbor molecules. Chakraborty et al. studied the reaction dynamic of an isolated molecule. In contrast, our NNP-MD simulations resolve the decomposition of the bulk RDX crystal. The neighbor molecules around the RDR might impose intense steric effects on the ring-opening reactions prohibiting the progress of ring opening, and this effect are discussed latter. In previous DFT studies , the HONO pathway is another channel for RDX decomposition, where H atoms migrate to -NO2 in RDX and undergoes a direct elimination of HNO2. This pathway is observed in our NNP-MD simulations, but its frequency is very low (e.g. In addition, we further perform MD simulations on RDX in the gas phase using NNP, where the densities are selected as 0.5 and 0.1 g/cm . The simulations are performed under an NVT ensemble at 2500 K. The results from RDX crystals (1.8 g/cm 3 ) are also included for comparison. Figure shows the flux of N-N homolysis, H abstraction, and ring-opening reactions of RDX and RDR molecules. As discussed above, RDX crystals are mainly consumed through the N-N homolysis, while the proportion of H abstraction and ring-opening reaction increase for RDR molecules. As the density decreases, the proportion of ring-opening reaction increases significantly (from 6% to 26% for RDX, 17% to 34% for RDR). The proportion of N-N homolysis, and H abstraction reactions decrease with the system density. Such behaviors are attributed to the effects of neighbor molecules. At high-density conditions, the ring-opening reaction is hindered by the neighbor molecules due to the steric effects.