Pressurehyphen;induced splitting and collapsing of the CN stretching vibration band in the Raman spectrum of crystalline Hg(CN)2

摘要

Raman spectra of crystalline Hg(CN)2have been measured as a function of pressure up to 45.1 kbar. The CN stretching band appears as a singlet in the pressure range 0ndash;16 kbar and its frequency exhibits a nonlinear pressure dependence. It becomes a doublet and shifts to lower frequency at 20 kbar where a structural phase transition takes place. The intensity of the highhyphen;frequency component of the doublet decreases with increasing pressure and totally disappears at 40 kbar where a second structural phase transition takes place. The phase transition at 20 kbar is driven by the intramolecular distortion and the intermolecular coordination processes and the transition at 40 kbar is triggered by an increase of symmetry of the molecular configuration.