We performed elasticity and Raman scattering measurements of ortho-FeSiO3 up to ∼7.5 GPa. The velocities of the P and S waves were measured in conjunction with in situ X-radiation techniques. Above 5 GPa, the velocity of the S wave, but not the P wave, exhibited strong softening while the averaged crystal structure, as indicated by X-ray diffraction, maintained an orthorhombic symmetry. Within the same pressure range, the Raman shifts showed systematic increasing as a function of pressure. Based on the results of both Mg and Fe end-member orthopyroxenes, the observed velocity anomalies marked the onset of a phase transition to the high-pressure phase. The experimental results in this study provide insight into lattice dynamic behavior in terms of the composition effect at the onset of the phase transition in the orthopyroxene group under compression.
All Science Journal Classification (ASJC) codes