High-pressure structural studies of energetic compounds

Abstract

The phase diagram of the energetic material hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has been explored using X-ray and neutron diffraction from ambient pressure to 8 GPa. Two phases of RDX have been structurally characterized. The high-pressure γ-polymorph exists above 4 GPa while the metastable β-polymorph has been isolated from the high boiling point solvent nitrobenzene. Interestingly, neutron diffraction measurements at high pressures and high temperatures show that the β-polymorph isolated under ambient conditions is not the same polymorph as can be accessed at high pressures and temperatures.

Keywords:

• phase diagram
• phase transition
• energetic material
• X-ray
• neutron
• diamond anvil cell

Acknowledgements

We thank Dstl and EPSRC for contributions toward a studentship (DIAM), the STFC for the provision of neutron beam time, the Leverhulme Trust for a fellowship (IDHO) and MOD WPE for funding under the terms of contract RD028-06366. We also thank A. Longmuir and I. Dickson of Lothian and Borders Police for advice on security and storage of energetic materials.