Polarized Raman spectroscopy and lattice dynamics of potassic-magnesio-arfvedsonite
- 44 Downloads
We report polarized Raman spectra from potassic-magnesio-arfvedsonite in all informative scattering configurations. On the basis of the polarization selection rules, several Ag vibrational modes have been identified. The Bg modes, however, are below the detection limits of the Raman spectrometer. The OH stretching band is situated between 3630 and 3750 cm−1, and its spectral shape is typical of amphiboles with high occupancy of the A site. It is composed of seven overlapping but resolvable subbands, which stem from occupied A-site configurations M(1)M(1)M(3)–OH–A(K/Na)–WOH and M(1)M(1)M(3)–OH–A(K/Na)–WF, as well as from vacant A-site configurations M(1)M(1)M(3)–OH–A□–WOH, with different Mg and Fe occupancy of the M(1) and M(3) sites. The experimental Raman spectra are compared with the results of theoretical calculations based on a shell-model force-field and a bond polarizability model. The simulated partial Raman spectra allowed us to assign many low-frequency Raman bands to stretching vibrations involving specific cation-oxygen bonds, as well as the higher-frequency modes of the Si–O skeleton. On the basis of our calculations we hypothesize that the Raman bands at 467, 540 and 589 cm−1 are related to a superposition of M(2)Fe3+–O bond stretching and Si–O–Si bending vibrations.
KeywordsAmphibole Arfvedsonite Potassic-magnesio-arfvedsonite Raman spectroscopy Lattice dynamics calculation
This work was supported by the Grant DH 14/8 of the National Science Fund of the Ministry of Education and Science of Bulgaria.
- Apopei IA, Buzgar N (2010) The Raman study of amphiboles. Sci Ann Alexandru Ioan Cuza Univ Iasi Geol 56:57–83Google Scholar
- Della Ventura G, Robert J-L, Bény J-M, Raudsepp M, Howthorne FC (1993) The OH–F substitution in Ti-rich potassium richterite: Rietveld structure refinement and FTIR and micro-Ramans spectroscopic studies of synthetic amphiboles in the system K2O–Na2O–CaO–MgO–SiO2–TiO2–H2O–HF. Am Mineral 78:980–987Google Scholar
- Dyulgerov M, Oberti R, Platevoet B, Kadiiski M, Rusanov V (2018) Potassic-magnesio-arfvedsonite—KNa2(MgFe2+Fe3+)5Si8O22(OH)2: mineral description and crystal chemistry. Mineral Mag (accepted) Google Scholar
- Fornero E, Allegrina M, Rinaudo C, Mazziotti-Tagliani S, Gianfafagna A (2008) Micro-Raman spectroscopy applied on oriented crystals of fluoro-edenite amphibole. Per Mineral 77(2):5–14Google Scholar
- Hawthorne FC, Ventura GD (2007) Short-range order in amphiboles. In: Hawthorne FC, Oberti R, Ventura GD, Mottana A (eds) Review in mineralogy and geochemistry, vol 67. Mineralogical Society of America and Geochemical Society, Washington DC, pp 173–222Google Scholar
- Leissner L, Schlüte J, Horn I, Mihailova B (2015a) Crystal chemistry of amphiboles by Raman spectroscopy. Periodico di Mineralogia ECMS 2015:109–110Google Scholar
- Nakamoto K (2009) Infrared and Raman Spectra of inorganic and coordination compounds. Part A: theory and applications in inorganic chemistry. Wiley, New York, pp 192–204Google Scholar