Raman and X-ray investigations of LiFeSi2O6 pyroxene under pressure

In situ Raman spectroscopy at high pressure was utilized to follow the phase transition of a synthetic sample of Li‐aegerine pyroxene (LiFeSi2O6) from its low‐pressure (C2/c) phase to its high‐pressure (P21/c) phase. The phase change occurred between 0.7 and 1 GPa and was accompanied by a change in coordination of the Li atom from 4 to 5, which was confirmed by single‐crystal X‐ray diffraction. This is the first report of the Raman spectrum of Li‐aegerine in the P21/c phase. As was previously observed with other pyroxenes, additional changes in the Raman spectra were observed at pressures higher than the phase transition, including the splitting of the peak near 700 cm−1, which has traditionally been utilized to indicate the phase transition. Comparisons with the Raman spectra of spodumene in both symmetries are utilized for a discussion of modes. Copyright © 2005 John Wiley & Sons, Ltd.