The effect of pressure on the Raman spectra of mercurous chloride and bromide

The Raman spectra of powdered mercurous chloride and bromide have been measured at zero pressure and up to 16 kbar. At low pressure there are many bands that are forbidden by the crystallographic symmetry I4/mmm, and so the apparent symmetry arises by disorder. One forbidden band was studied under pressure and it increased greatly in intensity. The disorder therefore increases in amplitude with increasing pressure. The disorder is probably related to the structures of the low‐temperature phases.