RAMAN SPECTROSCOPY OF RDX SINGLE CRYSTALS UNDER STATIC COMPRESSION

To gain insight into the high pressure response of energetic crystal of RDX, Raman measurements were performed under hydrostatic compression up to 15 GPa. Several distinct changes in the spectra were found at $4.0±0.3 GPa,$ confirming the α‐γ phase transition previously observed in polycrystalline samples. Symmetry correlation analyses indicate that the γ‐polymorph may assume a space group isomorphous with a point group $D2h$ with eight molecules occupying the $C1$ symmetry sites, similar to the α‐phase. It is proposed that factor group coupling can account for the observed increase in the number of modes in the γ‐phase.