Force Field Parameters for Ammonium Perchlorate Validated Using Surface Energies and Applied to Interactions with Polymer Binder

Force field parameter sets for ammonium perchlorate (AP) previously optimized to reproduce crystal lattice parameters were evaluated by their agreement with 0 K surface energies of the (210), (001), (010), (100), (101), and (011) facets determined by quantum mechanical (QM) methods based on first-principles density functional theory calculations. All of the parameter sets matched the qualitative ordering of least-to-highest surface energies predicted by QM, except for the (101)–(100) surface energy comparison. A force field parameter set with the best overall agreement with the absolute surface energies computed by QM methods was selected and used to investigate the interactions of the (001) and (210) surfaces of AP with the polymer binder hydroxyl-terminated polybutadiene (HTPB). The AP–HTPB interfacial energies determined by molecular simulations qualitatively agreed with the experimental observations. The simulations in this work also corroborate the experimental findings that suggest that hydroxyl groups interacting with the AP surface are responsible for the surface dependence of the AP–HTPB interfacial tension.