Pressure dependence of Raman-active phonons of CaBr2

Abstract Raman scattering measurements have been carried out in anhydrous CaBr2 under variable pressure, in the range 0–100kbar using nitrogen as pressure transmitting medium. At low pressures (p<25kbar) five Raman-active phonons have been identified, out of the six expected for the orthorhombic D12 2h structure; plots of the phonon frequencies against the pressure show steep slopes up to this pressure. Above 25kbar, substantial changes of the spectrum (including an increase of the number of phonon peaks) have been observed, accompanied by alterations of the phonon frequency slopes. The variation of the Raman spectrum suggests that some kind of high-pressure structural change occurs in the crystal.