High-pressure studies of polymorphs of CL-20 (hexanitrohexaazaisowurtzitane)

The aim of this proposal is to explore the effects of elevated pressures on the crystal structures of three polymorphs of CL-20 - a powerful explosive that is attracting increasing attention. The results of these studies will complement an ongoing single crystal X-ray diffraction study and will provide valuable information on the effects of pressure on CL-20, particularly on conformational changes, phase transitions, and intermolecular hydrogen-bonding interactions. The study will follow the structural evolution of three polymorphs of CL-20 with pressure. The results will also enable computational studies to explore the sensitivities of the different polymorphs of CL-20 towards initiation by shock and impact using the vibrational up-pumping model that assesses how energy is transfered through the low-energy phonon bath modes to reach the molecular vibrations. Most importantly, these studies will improve our understanding of the factors that influence the sensitivity of energetic materials to initiation by shock and impact, thereby enabling the subsequent design of new, safer energetic materials that are less prone to accidental initiation during manufacture, storage, and transport. In particular, the results will be highly relevant to UK MoD who have overall responsibility for the safety of UK munitions.