Raman spectroscopy of Cs2HgBr4 at high pressure: effect of hydrostaticity

Raman spectra have been measured on Cs2HgBr4 as a function of pressure, degree of hydrostaticity and location in the sample chamber. In the absence of a pressure-transmitting medium the title compound transforms reversibly into an amorphous phase at about 9 GPa, and this throughout the sample chamber. When argon is used as pressure-transmitting medium in a similar pressure range, different areas (with an approximate radius of 2 µm) of the pressure chamber yield dissimilar Raman spectra, varying from complete amorphization to a crystal-to-crystal transition. The results from this Raman study are combined with previous x-ray diffraction results and simulations on the same compound to give a comprehensive picture of the formation of a ferroelastic glass state.