Superspace description of wagnerite-group minerals (Mg,Fe,Mn) 2 (PO 4 )(F,OH)

Lazic, Biljana; Armbruster, Thomas Michael; Chopin, Christian; Grew, Edward S.; Baronnet, Alain; Palatinus, Lukas (2014). Superspace description of wagnerite-group minerals (Mg,Fe,Mn) 2 (PO 4 )(F,OH). Acta crystallographica Section B, B70(2), pp. 243-258. International Union of Crystallography 10.1107/S2052520613031247

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Reinvestigation of more than 40 samples of minerals belonging to the wagnerite group (Mg, Fe, Mn)2(PO4)(F,OH) from diverse geological environments worldwide, using single-crystal X-ray diffraction analysis, showed that most crystals have incommensurate structures and, as such, are not adequately described with known polytype models (2b), (3b), (5b), (7b) and (9b). Therefore, we present here a unified superspace model for the structural description of periodically and aperiodically modulated wagnerite with the (3+1)-dimensional superspace group C2/c(0[beta]0)s0 based on the average triplite structure with cell parameters a [asymptotically equal to] 12.8, b [asymptotically equal to] 6.4, c [asymptotically equal to] 9.6 Å, [beta] [asymptotically equal to] 117° and the modulation vectors q = [beta]b*. The superspace approach provides a way of simple modelling of the positional and occupational modulation of Mg/Fe and F/OH in wagnerite. This allows direct comparison of crystal properties.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Armbruster, Thomas Michael

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

2052-5206

Publisher:

International Union of Crystallography

Language:

English

Submitter:

Sarah Antenen

Date Deposited:

11 Aug 2015 15:38

Last Modified:

02 Aug 2017 08:53

Publisher DOI:

10.1107/S2052520613031247

BORIS DOI:

10.7892/boris.70811

URI:

https://boris.unibe.ch/id/eprint/70811

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