The aims of this proposal are to explore the high-pressure, high-temperature behaviour of 3important energetic materials - CL-20, HMX and TATB. These experiments are expected toidentify and structurally characterise new forms of these materials, and offer the potential for therecovery of metastable forms to ambient conditions. These recovered forms may exhibitenhanced properties such as reduced sensitivity or higher density. The studies will also providestructural 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 the modelling of the performance characteristics of these materials.