Crystal-field theory calculations for Fe2+ Ions in bronzite,augite, and olivine |
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| Authors: | Takahiro Hiroi Hiroshi Takeda |
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| Institution: | 1. SN3, NASA/JSC, 77058, Houston, TX, USA
2. Mineralogical Institute, Faculty of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113, Tokyo, Japan
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| Abstract: | Crystal-field theory was applied to Fe2+ ions in three types of silicates in an attempt to assign all the major absorption bands with only one parameter to adjust. Coulomb potential energy field were calculated by Fourier method based on all the actual atomic coordinates refined by X-ray diffraction studies. Perturbed d-electron splitting energies of the central Fe2+ ion were calculated by introducing Configuration Interaction (CI) method for the lowest energy spectral states. All the major absorption bands observed in powdered bronzite, augite, and olivine, were assigned to the transitions between those calculated energy levels by optimizing only one parameter that expresses expansion or contraction of d-electron cloud. The result of the calculations gives almost the same assignments as the other previous works for bronzites, different assignments for augites, and a possibility of the existence of the fourth band hidden in the composite 1-μm band of olivines. |
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