Raman and X‐ray investigations of LiFeSi 2 O 6 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 (LiFeSi 2 O 6 ) from its low‐pressure ( C 2/ c ) phase to its high‐pressure ( P 2 1 / 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 P 2 1 / 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.