The initial reaction mechanism of FOX-7 under high temperature and high pressure

In recent years, FOX-7 has attracted great interest due to its excellent performance. The initial decomposition mechanism of FOX-7 (ε phase) at high temperature and pressure is simulated by ab initio molecular dynamics. We mainly studied the initial reaction of FOX-7 under extreme conditions of 10 GPa and 700-3000 K. When the pressure is constant, FOX-7 shows different decomposition mechanisms as the temperature increases. At lower temperatures, hydrogen is transferred first. As the temperature increases, the transfer of hydrogen and the breakage of the C-NO2 bond leading to the generation of acid are the main initial decomposition pathways. The energy barrier for hydrogen transfer is lower than that of C-NO2 bond breaking, which was confirmed by a single-molecule transition state search. Thus, the correctness of the decomposition mechanism obtained by molecular dynamics is proved. Different from previous studies, this paper considers both temperature and higher pressure, providing a reference for the initial reaction mechanism of FOX-7 under extreme conditions.