The Calcite Raman spectrum and its interpretation are presented below.
Calcite sample data
| Description: | Calcite mineral sample |
|---|---|
| Mineral: | Calcite |
| RAMAN ID: | RAMAN5413 |
| Ideal chemistry: | CaCO3 |
| Source: | Grigore Cobălcescu Museum |
| Locality: | Mexic |
| Owner: | Department of Geology – Alexandru Ioan Cuza University of Iasi |
Calcite sample image
Raman spectrum of Calcite
Main Raman bands of Calcite
| Wavenumbers (cm-1): | 1092vs, 715w, 285m |
|---|
Raman parameters
| Instrument settings: | Raman spectrograph HE 532nm (Horiba Jobin-Yvon) |
|---|---|
| Spectral resolution: | 2 cm-1 |
| Conditions of measurement: | at room temperature |
Interpretation of Raman spectrum of Calcite
The intense band (ν1) of calcite spectrum corresponds to the symmetric stretching of CO3 group at 1092 cm-1. The ν2 (asymmetric deformation) vibration mode is not active in Raman. The values attributed to ν3 (asymmetric stretching) mode are 1437 cm-1 and ν4 (symmetric deformation) mode at 715 cm-1. Symmetric deformation or symmetric bending, also applies to asymmetric deformation.
The observed vibrational bands of calcite 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 and Apopei, 2009).
| Buzgar and Apopei, 2009 | Gunasekaran et al., 2006 | Free CO32- | Assignment |
| 89 | R(CO3) | ||
| 162 | T(Ca, CO3) | ||
| 285 | 288 | T(Ca, CO3) | |
| 715 | 716 | 680 | ν4 symmetric CO3 deformation |
| 879 | ν2 asymmetric CO3 deformation | ||
| 1092 | 1092 | 1063 | ν1 symmetric CO3 stretching |
| 1437 | 1437 | 1415 | ν3 asymmetric CO3 stretching |
| 1749 | 1754 | ν1 + ν4 |
The lower wavenumbers of calcite (285 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 1749 cm-1 may be regarded as the combination band of ν1 + ν4 (Gunasekaran et al., 2006).
References for the Raman spectrum of Calcite
- BUZGAR 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]
- GUNASEKARAN S., ANBALAGAN G., PANDI S. (2006) – Raman and infrared spectra of carbonates of calcite structure. Journal of Raman Spectroscopy, 37, p. 892-899 [link]