Raman spectroscopy and X-ray diffraction of diphenylphosphoryl azide under high pressures

Diphenylphosphoryl azide ((C6H5O)(2)P(O)N-3, DPPA) was studied by in situ Raman scattering spectroscopy and synchrotron angle-dispersive X-ray diffraction (ADXRD) technologies up to 11.6 GPa at room temperature. The analyses of Raman spectra revealed that the liquid DPPA transformed from Phase I to Phase II at 0.4 GPa and went to Phase III at 1.3 GPa. The first phase transition was attributed to the change of molecular conformation, and the second phase transition was induced by the deformation of benzene rings. The XRD results suggested that DPPA remained in a liquid state during the two phase transitions. The azide group became increasingly asymmetric under pressure and decomposed at 11.6 GPa. The low decomposition pressure of the azide group is conducive to the formation of polymeric nitrogen. Exploring the behaviors of the azide group under pressure might be helpful for understanding the potential application of DPPA in the synthesis of high energy density materials (HEDMs).

Automated summary

The behavior of Diphenylphosphoryl azide (DPPA) under pressure was studied using in situ Raman scattering spectroscopy and synchrotron angle-dispersive X-ray diffraction. The study revealed that DPPA undergoes two phase transitions at 0.4 GPa and 1.3 GPa, accompanied by changes in molecular conformation and deformation of benzene rings. XRD results showed that DPPA remains in a liquid state during the phase transitions. The decompositon of the azide group occurs at 11.6 GPa, suggesting the potential formation of polymeric nitrogen. Understanding the behavior of the azide group under pressure is important for the synthesis of high energy density materials using DPPA.