Probing Equations of State and Novel Phases of Energetic Crystals via First Principles Simulations

Energetic crystals are widely used in military and industrial applications. Modeling the shock propagation and initiation of energetic materials rely on the unreacted equation of state which can vary greatly if there is a phase transition. Many current models do not include phase transitions which can be difficult to detect in experiment. Furthermore, most first-principles based models use density functional theory that gives a poor description of dispersion. In this work, pressure-induced phase transitions and equations of state of energetic crystals are investigated using first-principles based approaches ranging from density functional theory to post-Hartree-Fock perturbative methods that give a better description of dispersion. Novel high-pressure phases are probed using crystal structure prediction method USPEX. The feasibility of using perturbative and hybrid methods to predict phase transition pressures is investigated.