SPAFMSR



Buzgar N., Apopei A. I., Buzatu A. (2009) - Romanian Database of Raman Spectroscopy (http://rdrs.uaic.ro)
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Formula: |
Fe2+CO3 |
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Crystal Data: |
Crystal System: Trigonal - Hexagonal Scalenohedral |
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Point Group: 3 2/m |
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Cell Data: |
Space Group: R 3c, a = 4.72, c = 15.46, Z = 6 |
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Density (calc.) = 3.87 and V = 298.28 Å3 |
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Element color: Fe, C, O |
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Sample no. 5455 from the "Mineralogy and Petrography Museum Grigore Cobălcescu" of "Alexandru Ioan Cuza" University, Iaşi. Origin: Lobenstein - Germany. Click image to enlarge |
The Raman spectrum of siderite is characterized by the same band of calcite at 1087 cm-1 corresponding to the symmetric stretching of CO3 group. The band at 737 cm-1 corresponds to the ν4 (O-C-O in-plane bending) vibrational mode and 1442 cm-1 to ν3 mode.
The observed vibrational bands of siderite compared with well-documented values are listed below. The minor shift in positions may be due to the effects of natural impurities present in the sample.
Buzgar et al., 20091 | Beny, 1991 | Free CO32- | Assignment |
R(CO3) | |||
190 | T(Fe, CO3) | ||
289 | 294 | T(Fe, CO3) | |
514 | 506 | Fe-O | |
737 | 731 742 |
680 | ν4 symmetric CO3 deformation |
879 | ν2 asymmetric CO3 deformation | ||
1087 | 1087 | 1063 | ν1 symmetric CO3 stretching |
1442 | 1415 | ν3 asymmetric CO3 stretching | |
1729 | 1726 1733 |
ν1 + ν4 |
The lower wavenumbers of siderite (289 cm-1) observed in the above table, arise from the external vibration of the CO3 group that involve translatory oscillations of the group (relative translations between the cation and anionic group). In this spectrum are no values below 200 cm-1 because the spectral range is between 200 - 3400 cm-1.
A weak line observed at 1729 cm-1 may be regarded as the combination band of ν1 + ν4. This interpretation is also favoured by Schaefer et al. However and Krishnan assigned this band to 2ν2. The spectrum also presents a band at 514 cm-1, wich may be assigned to the vibration of a Fe-O bond.
The positions of the observed Raman bands are in agreement with those reported by Beny C., 1991.
• The Mineralogy Database [link]
• Crystal data (.cif file) from the American Mineralogist Crystal Structure Database [link]
• 1BUZGAR N., APOPEI A. I. (2009) - The Raman study on certain carbonates. Analele Stiintifice ale Universitatii “Al. I. Cuza” - Iasi, Tome 55, issue 2, 97-112 [link]
• BENY C. (1991) - Societe Francaise de Mineralogie et de Cristallographie - Base donnees de spectres Raman. Siderite [link]