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K2CO3: Crystal structure | Sample photo | Raman spectrum | Interpretation | References

Crystal structure of K2CO3

Formula:

K2CO3

Crystal Data:

Crystal System: Hexagonal - Dihexagonal Pyramidal

Point Group: 6mm

Cell Data:

Space Group: P 63mc, a = 5.215, c = 6.584, Z = 2

Density (calc.) = 2.27 and V = 155.07 Å3

K2CO3 sample
K<sub>2</sub>CO<sub>3</sub>

Synthetic sample.




Click image to enlarge

Raman spectrum and vibrations of K2CO3
Element color: C, O Toggle Grid Toggle Coordinates Reverse Spectrum

Click to in the Raman spectrum. To see the vibrations click on one of them (highlight region) and it (the selected vibration) will appear on the right side of the Raman spectrum.
Below spectra are various settings, and other vibrations of K2CO3 (which are not present in this spectrum).
You have the possibility to zoom in the spectrum by selecting a spectral region you need to be increased (along axis x); to zoom keep the left mouse-click continously pressed, drag (to left or to right) and release the left button. To return to the initial size spectrum, press the right click on the spectrum -> Zoom -> Reset View.

Model type:
Sticks Ball-and-Sticks (1) Ball-and-Sticks (2) CPK (Spacefill)

Orientation:
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CO3 polyhedra on CO3 polyhedra off
Vibrations:
702 cm-1 - ν4b (E') 677 cm-1 - ν4a (E') 1063 cm-1 - ν1 (A'1) 1374 cm-1 - ν3a (E') 1426 cm-1 - ν3b (E')

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Download spectrum:
Raman spectrum .txt Raman spectrum .spc


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Interpretation of Raman spectrum of K2CO3 (Gregoryite)

The Raman spectrum of K2CO3 shows a couple of bands at 1026 and 1063 cm-1 that may be attributed to the ν1 symmetric stretching mode. The two bands may be explained by the presence of the molecules belonging to two structures, C2v bidentate form and D3h, in agreement with the theoretical values calculated by Koura et al. (1996). The ν2 vibration mode is not Raman active. The bands at 1374 cm-1 and 1426 cm-1, can be assigned to ν3a respectively ν3b. To the ν4 mode (doubly degenerate symmetric bending) are attributed the values of 677 cm-14a) and 702 cm-14b). The spectrum also presents three bands at 237 cm-1, 287 cm-1 and 484 cm-1, which may be assigned to the external vibration modes between the cation and anionic group (T(K,CO3)).

The frequency of the detected bands is reported in below table.


Buzgar et al., 20091 Koura, 1966 Koura, 1966 Assignment
Calculated Measured
237
288
484
76, 85 122,
252, 278, 291
126, 141,
192
T(K,CO3)
677 688 692 ν4a (E') symmetric deformation
702 706 697 ν4b (E') symmetric deformation
1026
1063
1025 1043
1064
ν1 (A'1) symmetric stretch
1374 1385 1405 ν3a (E') asymmetric stretch
1426 1557 ν3b (E') asymmetric stretch
NO = not observed; NA = not assigned
References

• The Mineralogy 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]

• KOURA N., KOHARA S., TAKEUCHI K., TAKAHASI S., CURTISS L. A., GRIMSDITCH M., SABOUNGI M. L. (1996) - Alkali carbonates: Raman spectroscopy, ab initio calculations and structure. Journal of Molecular Structure, 382, p. 163-169 [link]