The aims of this proposal are to explore the high-pressure, high-temperature behaviour of 2 important energetic materials - N-guanylurea dinitramide (FOX-12) and 2,4-dinitroanisole (DNAN). These experiments are expected to identify and structurally characterise new forms of these materials, and offer the potential for the recovery of metastable forms to ambient conditions. These recovered forms may exhibit enhanced properties such as reduced sensitivity or higher density. The studies will also provide structural information as a function of pressure with a particular focus on intermolecular interactions involving H-atoms. Such interactions are important in the intermolecular transfer of energy and have implications for the shock sensitivity of these materials. Phase transitions observed under these extreme conditions also have important implications for modelling performance.