Confirmation of the Structural Phase Transitions in XeF₂ under High Pressure

Abstract

Unique structures and properties will be introduced upon compression. To figure out the high pressure crystal structure of XeF2, in situ synchrotron X-ray diffraction, Raman spectra, UV–vis absorption spectra, and theoretical calculations have been performed up to 86 GPa. The structural dispute between reported experimental and theoretical results is settled by this study. The experimental and theoretical Raman spectra results indicated that the ambient structure of XeF2 (I4/mmm) transformed into a Immm structure at 28 GPa. Then this Immm structure transformed into Pnma structure at 59 GPa. The Rietveld refinement of the XRD results was in accordance with our Raman study. The optical absorption spectra revealed a reduction in the band gap as pressure increases. The reduction in the band gap decreases to 1.83 eV at 82 GPa while the color of the sample is getting dark. Our results provide a new insight into the high pressure behavior of noble gas compounds with the example of XeF2.