Vibrational spectroscopy at very high pressures. Part 15. Raman and infrared study of mercury(II) chloride

Abstract

Raman spectra at 295 and 150 K, and i.r. spectra at 295 K, are given for HgCl₂(phases I, II, and IV) at hydrostatic pressures up to 30 kbar. The ultramicrosampling technique used with the diamond-anvil high-pressure cell is described. The small spectral differences between phases I and IV are interpreted in terms of a second-order transition with retention of space group. The profound spectral differences accompanying the IV–II transition are accommodated by postulating that HgCl₂(II) has the cubic CO₂(T_h ⁶) structure. Mechanisms for the transitions are proposed.