Reactive molecular dynamics simulations on the decomposition process of 1,3,5-trinitro-1,3,5-triazine crystal under high temperatures and pressure

Context Reactive molecular dynamics simulations were performed to study the decomposition processes of 1,3,5-trinitro-1,3,5-triazine (RDX) crystal under high temperatures (2100, 2400, 2700, and 3000 K) and detonation pressure (34.5 GPa) and 0 GPa. It is found that the initial decomposition paths of RDX under different temperatures coupled with detonation pressure are similar, which is due to the N-NO2 bond breakage to release NO2. The formation rates of N-2 and H2O are significantly affected by temperature, while those of CO2 are less influenced. The C atoms finally formed C clusters. As the temperature rises, the decomposition speeds up, indicating that the high temperature accelerates the decomposition. Applying pressure can reduce the reaction energy barrier and accelerate the decomposition.Methods The RDX model was constructed using the Materials Studio 7.0 package. All MD simulations were performed based on the ReaxFF force field in the LAMMPS software package, and the crystals were visualized using the OVITO software package. The time step was 0.1 fs, and the total MD simulation time was 200 ps. DFT calculations were carried out at the B3LYP/6-311G(d,p) level using the Gaussian 09 package.