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Faulques, E., Perry, D. L. & Kalashnyk, N. (2018) Vibrational spectroscopy of a crystallographically unsettled uranyl carbonate: Structural impact and model. Vib. Spectrosc. 99 184–189. 
Added by: Richard Baschera (2018-12-20 08:53:58)   Last edited by: Richard Baschera (2018-12-20 08:58:39)
Type de référence: Article
DOI: 10.1016/j.vibspec.2018.10.004
Numéro d'identification (ISBN etc.): 0924-2031
Clé BibTeX: Faulques2018
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Mots-clés: Carbonate, dft, infrared reflectance, infrared spectroscopy, liebigite, minerals, nitrate, oxygen bond lengths, photoluminescence, Raman scattering, uranium, Voglite, Water
Créateurs: Faulques, Kalashnyk, Perry
Collection: Vib. Spectrosc.
Consultations : 4/372
Indice de consultation : 4%
Indice de popularité : 1%
Room-temperature vibrational and photoluminescence (PL) spectra of a natural, rare hydrated calcium copper uranyl carbonate mineral, voglite (Ca2Cu(UO2)(CO2)(4)center dot 6H(2)O) are recorded and discussed in details. Vibrational spectroscopy gives information about the structure of voglite, which is still missing due to its unknown crystallographic features. By comparison with other uranyl carbonates and sulfates, a strong Raman line occurring at 834 cm(-1) is assigned to the nu(1)(UO2)(2+) symmetric stretching vibration rather than to the nu(2)(CO3)(2-) out-of-plane bending vibration. The v(3)(UO2)(2+) antisymmetric stretching vibration is tentatively identified at 897 cm(-1) from infrared (IR) spectroscopy. Several well resolved bands found at 1074,1092, 1381, 1566 cm(-1) in the Raman and 1046, 1114, 1145, 1376, 1426, 1510, 1561 cm(-1) in the IR are ascribed to symmetric and antisymmetric stretching motions of the carbonate units. The presence of all these intense vibrational bands points to different C-O bond lengths. The infrared water band is well structured, suggesting a few different -OH moieties in the crystal. Original micro-PL spectra show a manifold of vibronic features whose energy spacing is close to the frequency of the symmetric O-U-O stretching vibration and confirms the uranium origin of the most intense Raman band. The study suggests that voglite structure has no inversion centers, a low symmetry, and contains molecular units similar to those of the parent phases, andersonite or liebigite, like uranyl tricarbonate clusters (UTC). The existence of these UTCs in voglite is confirmed by density functional theory calculations. A new assignment of all vibrational modes is proposed.
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