Early Events When Heating 1,1-Diamino-2,2-dinitroethylene: Self-Consistent Charge Density-Functional Tight-Binding Molecular Dynamics Simulations

Abstract

A self-consistent charge density-functional tight-binding method combined with molecular dynamics (MD) simulations and static density functional theory (DFT) calculations is employed to reveal the initial steps responsible for the thermal decay of the low sensitive and high energetic material (EM) 1,1-diamino-2,2-dinitroethylene (FOX-7). Constant temperature heating and temperature-programmed heating are accounted in our MD simulations to resemble the practice. We find that the heating style has an impact on the initial decomposition mechanism of FOX-7. The N–O bond rupture to produce an O radical is observed for the first time in the temperature-programmed heating simulation from 300 to 3000 K, together with the C–NO2 bond cleavage. We also first capture the intra- and intermolecular hydrogen transferred structures in our constant temperature heating simulation at 3000 K, and in this case, the NO2 partition serves as another kind of primary step for thermally decaying FOX-7 too. Static DFT calculations s...