Decomposition of RDX and 3-HMX

Two decomposition processes suggested on the base of experiment by B.M. Rice et al. Ref. 7 and Shalashilin Thompson Ref. 3, were confirmed by the analysis of dynamic trajectories for both molecules RDX and p-HMX. However our results of molecular dynamics simulations did not confirm the conclusion of Rice, see Ref. 7, that the reaction R1 (RDX - C3H6N504+ N02) occurs at low temperatures and the reaction R2 (RDX - 3CH2NN02) is more probable at high temperatures. Analysis of 40 dynamic trajectories for RDX and P-HMX showed that both reactions occur at low and high temperatures with the same probability. Dynamic simulations show that most probable decomposition process is the combination of reaction R1 and R2. In such a case the first N02 group is released neither after first C-N bond rupture (Rl), nor after all C-N bond rupture (R2), but after the second (in case of p-HMX second or third) C-N bond rupture according to the scheme C-N - C-N - C-N - N-N02 — C-N. 

Two examples of the dynamic trajectories (the time dependence of the kinetic energy) for the molecule RDX are presented in the Fig. 3 and 4, where the Fig. 3 illustrates the reaction pathway Rl and the Fig. 4 shows the trajectory for the reaction R2. Arrows mark the points on the dynamic trajectory corresponding to the rupture of C-N and N-N02 bonds. Fig. 5 shows the example of trajectory for p-HMX, where the decomposition process is the combination of Rl and R2 reactions. Anyway the character of dynamic trajectories and consequently the character of molecular decomposition is very similar for RDX and p-HMX. 

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