Raman Spectroscopic and Visible Absorption Investigation of LiCrSi 2 O 6 Pyroxene under Pressure

Abstract

The first observation of the vibrational spectrum of the synthetic pyroxene Li-kosmochlor (LiCrSi₂O₆) is reported herein. The Raman and visible spectra are reported as a function of pressure. Though the pyroxene retains its P2₁/c symmetry, changes in the Raman spectra are observed between 6.8 and 7.7 GPa, possibly due to the formation of an additional bond between Li and O3 or some other transition that retains the mineral's P2₁/c space group. Splitting of the peak appearing at approximately 700 cm⁻¹, used to characterize the P2₁/c phase in other studies, is not observed. Comparison is made with the Raman spectra of LiAlSi₂O₆ and LiFeSi₂O₆ in the P2₁/c phase and the visible spectra of NaCrSi₂O₆ at high pressures.