Titre du document / Document title

The structure of metahohmannite, Fe₃₊2[O(SO⁴)²].4H²O, by in situ synchrotron powder diffraction

Auteur(s) / Author(s)

SCORDARI Fernando ; VENTRUTI Gennaro ; GUALTIERI Alessandro F. ;

Résumé / Abstract

Metahohmannite, Fe₃₊2[O(SO⁴)²].4H²O, is a hydrated sulfate of ferric iron that occurs in sulfate deposits in the desert areas of Northern Chile. The compound used for this study was obtained as a dehydration product of hohmannite, Fe₃₊2[O(SO⁴)²].(4+4)H²O. Intensities for the structure analysis were collected from a powdered sample using in situ synchrotron X-ray powder diffraction at ESRF (Grenoble, France). The structure was solved ab initio by profile deconvolution and the application of standard Patterson and difference Fourier maps. The structure was refined to R^p = 5.46% using the Rietveld method. Metahohmannite crystallizes in the triclinic system, space group PT with unit-cell parameters a = 7.3484(5) Å, b = 9.7710(6) Å, c = 7.1521(5) Å, a = 91.684(5)°, β = 98.523 (5)°, y = 86.390 (5)°, and Z = 2. The structure consists of four Fe₃₊ octahedra and four sulfate tetrahedra, which share vertices and edges to form a complex building block of Fe₃₊4[O²(SO⁴)⁴].8H²O composition. Such blocks are connected to form chains running parallel to the c axis. A complicated system of hydrogen bonds connects adjacent chains into a three-dimensional network. Finally, the crystal structures of metahohmannite, hohmannite, and amarantite are compared and the geometrical features discussed in detail.

Revue / Journal Title

The American mineralogist   ISSN 0003-004X   CODEN AMMIAY 

Source / Source

2004, vol. 89, n^o2-3, pp. 365-370 [6 page(s) (article)]

Langue / Language

Anglais

Editeur / Publisher

Mineralogical Society of America, Washington, DC, ETATS-UNIS  (1916) (Revue)

Localisation / Location

INIST-CNRS, Cote INIST : 503, 35400011919967.0160