Pressure-Driven Phase Transitions in Bulk HfS₂

The effect of hydrostatic pressure up to 27 GPa on the Raman scattering (RS) in bulk HfS$_2$ is investigated. There are two transformations RS spectra, which take place during compression at between 5.7 and 9.8 as well 12.8 15.2 GPa. Seven vibrational modes can be observed after transformation, compared four before transformation. change suggests structural material yet unknown nature. frequencies above transformation linearly with corresponding coefficients have been determined. other transition manifests itself a lineshape. While series well-defined under below transition, broad spectral bands seen higher pressure. overall lineshape spectra resembles that disordered materials. does not decompression, permanent nature high-pressure transition.