Pyrolysis mechanism of HTPB-containing ICM-107 composite: A DFTB molecular dynamics study

We theoretically demonstrated the thermal decomposition mechanisms of the ICM-107 and ICM-107/HTPB systems over the temperature range of 1000-3250 K. The results confirmed that the introduction of HTPB promoted the initial decomposition of ICM-107 molecules at lower temperatures, owing to hydrogen radicals generated during HTPB decomposition, but extended the time required for complete decomposition. In the ICM-107 system, the initial decomposition mechanisms involved the coupling of two ICM-107 molecules to form larger clusters, intermolecular hydrogen transfer, and ring-opening reactions. Furthermore, Arrhenius fitting confirmed that HTPB incorporation reduced the activation energy for the initial decomposition of ICM-107 molecules from 202.99 to 170.61 kJ/mol.

With the help of CP2K package, the self-consistent charge density functional tight-binding (SCC-DFTB) method was employed to perform calculations. The Broyden-Fletcher-Goldfarb-Shanno (BFGS) method was selected to perform the cell and geometry optimization. To improve the accuracy in describing the van der Waals forces, the DFT-D3 method was adopted. Molecular dynamics (MD) simulations were performed in the NVT ensemble using the canonical sampling through velocity rescaling (CSVR) thermostat. Meanwhile, the post-processing analysis of molecular dynamics trajectories was performed using ReaxTools to establish the initial decomposition pathways of the ICM-107 and ICM-107/HTPB systems.