High-Pressure Studies of Pentaerythritol Tetranitrate (PETN)

This proposal seeks to use powder neutron diffraction to explore the high-pressure structural behaviour of PETN (pentaerythritol tetranitrate), a crystalline material that is extensively used as an ingredient in many high explosive formulations such as Semtex. It has attracted considerable scientific attention due to its anisotropic sensitivity to shock-wave initiation. The study aims to determine the crystal structures of two high-pressure phases, PETN-III and PETN-IV, which have been previously identified at pressures above 8.5 GPa, but which have not been fully characterised. Determination of these structures will provide insight into the observed anisotropic sensitivity of PETN to shock-wave initiation. The results will also enable computational studies to explore the sensitivities of the different polymorphs of PETN towards initiation by shock and impact using a recently developed vibrational up-pumping model. These studies will therefore improve our understanding of the factors that influence the sensitivity to 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. The experiment will also provide excellent training in high-pressure neutron diffraction for a PhD student appointed as an ISIS Facility Development Studentship (“Energetic Materials at Extreme Conditions”).