High‐Pressure Vibrational Spectroscopy of Hexahydro‐ 1,3,5‐Trinitro‐1,3,5‐Triazine (RDX)

The molecular‐level response of RDX to hydrostatic compression was examined in a diamond anvil cell using Raman spectroscopy. The pressure‐induced alterations in spectral profiles of the C N stretching mode (886 cm⁻¹) were studied up to 8.3 GPa. At pressures near 4.4 GPa, several changes of the C N stretching mode become immediately apparent in Raman spectrum, such as large frequency shifts, line broadening, mode splitting, and intensity changes, which are associated with the α–γ phase transition and rearrangement between the RDX molecules. The high pressure Raman spectra changes of the C N stretching mode are indicative of an α–γ phase transition, and also suggest the lowering of molecular symmetry and crystal symmetry, which are expected to provide some insight into RDX molecular stability and decomposition.