Predictions of Properties of Energetic Materials from First Principles

Properties of solid energetic materials depend on a large extent on their crystal structure. Thus, the structure determines suitability of a given compound for defense purposes. Since there are no simple methods to predict crystal structures, such structures become known only after a given material has been synthesized and crystallized. The structures can be predicted from quantum mechanical calculations, but until recently the reliability of such predictions was very low. This situation has changed with the development of symmetry-adapted perturbation theory (SAPT) based on density-functional theory (DFT) description of monomers, an approach known as SAPT(DFT). The SAPT(DFT) potentials for dimers of energetic molecules were applied to predictions of properties of crystals of such molecules in a combined molecular packing, lattice minimization, and molecular dynamics simulations study. The properties of the cyclotrimethylene trinitramine (RDX) crystal predicted from first principles are in excellent agreement with experiment and the predictions are even somewhat better than achieved by empirical potentials fitted to the crystal experimental data. A similar work on the 1,1-diamino-2,2-dinitroethylene (FOX-7) crystal is in progress.