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Optical Absorption Spectra of (Mg,Fe)SiO3 Silicate Perovskites |
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| Authors: | Guoyin Shen Yingwei Fei Ulf Hålenius Yanbin Wang |
| Institution: | 1. Theoretical Geochemistry Program, Inst. of Earth Sciences, Uppsala University, Norbyv?gen 18B, 7526 3, Uppsala, Sweden 2. Center for High Pressure Research, Geophysical Lab., Carnegie Inst. of Washington, 5251 Broad Branch Road, 20015, Washington, DC, USA 3. Dept. of Mineralogy, Swedish Museum of Natural History, Box 50007, 10405, Stockholm, Sweden 4. Center for High Pressure Research, Department of Earth and Space Sciences, State University of New York at Stony Brook, 11794, New York, USA |
| Abstract: | Electronic absorption spectra have been measured at room temperature and pressure for polycrystalline samples of (Mg, Fe)SiO3 silicate perovskites synthesized by multi-anvil device. One strong near-infrared band at about 7000 cm-1 and several weak bands in the visible region were found. The near-infrared band at 7000 cm-1 is assigned to a spin-allowed transition of Fe2+ at the 8–12 coordinated site in perovskite. However, definite assignments of the weak bands in the visible region are difficult because of their low intensities and the scattering effect at the gain boundaries. Crystal field calculations for Fe2+ at different sites in perovskite have been carried out based on the crystal structure data. The results agree with the assignment of Fe2+ to the 8–12 coordinated site in perovskite. Crystal field stabilization energy of Fe2+ with coordination number of 8 in perovskite is 3332 cm-1 which is small compared to the octahedral site of magnesiowüstite (4320 cm-1), another important lower-mantle mineral. |
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