Molecular evolution mechanisms of FOX-7 under high-pressure shock on different crystal faces

To illustrate atomic-level insights into the physicochemical behavior of 1,1-diamino-2,2-dinitroethylene (FOX-7) under shock stimulation, this study applied pressure of 1 ​GPa–90 ​GPa on different crystalline faces through reactive molecular dynamics simulations and provided detailed information about the decomposition of FOX-7 at high pressure. The results show that the (010) face was much more compressible than the (100) face. Shocking the (010) and (100) faces yielded directional bulk moduli of 13.5 ​GPa and 29.1 ​GPa, respectively, and material sound velocities of 2.5 ​km· ​s−1 and 4.3 ​km· ​s−1, respectively. Under pressure below 60 ​GPa, the initial shock decomposition pathway of the (010) face was the intramolecular hydrogen (H) transfer, while that of the (100) face included dimerization and intermolecular H transfer. However, the difference in the reaction pathway faded away under pressure of around 80 ​GPa. Under all conditions, the main final small molecule fragments included N2 and H2O. Unlike thermal decomposition, in which FOX-7 yields NO2 via direct rupture, the high-pressure shock caused FOX-7 to produce carbon clusters with a few gaseous products.