Crystal structure and optical absorption spectra of LiCo(SO4)OH and its remarkable relationship to the Zn-Mn-silicate hodgkinsonite
- Autor(en)
- Manfred Wildner, Gerald Giester
- Abstrakt
Crystals of the compound LiCo(SO4)OH were synthesised at low-hydrothermal conditions, and the crystal structure was determined and refined from single crystal X-ray diffraction data. LiCo(SO4)OH crystallises monoclinic, space group P2(1)/c, Z = 4, a = 9.586(2), b = 5.425(1), c = 7.317(1) (A) over circle, beta = 109.65(1)degrees, V = 358.3 (A) over circle (3), wR2 = 0.0485 (2215 unique reflections, 78 variables). The structure is built from chains of edge-sharing, quite strongly bond-length and -angle distorted Co(OH)(3)O-3 octahedra (< Co-O > = 2.126 (A) over circle), which are further linked by common corners, hydrogen bonds, and by properly shaped SO4 tetrahedra (< S-O > = 1.476 A) to sheets parallel (100). These sheets are connected to a three-dimensional framework by sharing corners with distorted LiO4 polyhedra (< Li-O > = 1.956 (A) over circle). Apart from the isotypic sulfates of Mn2+ and Fe2+, only the molybdate LiCd(MoO4)OH crystallises isostructural with LiCo(SO4)OH. However, a very close structural relationship exists with the rare mineral hodgkinsonite, Zn2Mn(SiO4)(OH)(2), yielding crystal chemically very uncommon topological equivalents of Zn2+ equivalent to S6+ and Si4+ equivalent to Li+, aside from the expectable substitution Mn2+ equivalent to Co2+. Polarised optical absorption spectra of LiCo(SO4)OH reveal that the dominating spin-allowed T-4(1)(P) band system of Co2+ (d(7) configuration) is strongly split up and covers a prominent part (similar to 15,500-24,500 cm(-1)) of the visible spectral range, in accordance with the significant distortion of the Co(OH)(3)O-3 polyhedron. The spectra are interpreted in terms of the Superposition Model of crystal fields, yielding a new set of intrinsic and interelectronic repulsion parameters for Co2+.
- Organisation(en)
- Institut für Mineralogie und Kristallographie
- Journal
- Mineralogy and Petrology
- Band
- 117
- Seiten
- 317-324
- Anzahl der Seiten
- 8
- ISSN
- 0930-0708
- DOI
- https://doi.org/10.1007/s00710-022-00807-w
- Publikationsdatum
- 2023
- Peer-reviewed
- Ja
- ÖFOS 2012
- 105116 Mineralogie, 105105 Geochemie
- Schlagwörter
- ASJC Scopus Sachgebiete
- Geochemistry and Petrology, Geophysics
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/c1465487-9a66-4bac-b13f-669cd538fd25