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@ARTICLE{Gatta:859486,
author = {Gatta, G. Diego and Rotiroti, Nicola and Cámara, Fernando
and Meven, Martin},
title = {{O}n the labyrinthine world of arsenites: a single-crystal
neutron and {X}-ray diffraction study of cafarsite},
journal = {Physics and chemistry of minerals},
volume = {45},
number = {9},
issn = {1432-2021},
address = {Heidelberg},
publisher = {Springer},
reportid = {FZJ-2019-00339},
pages = {819 - 829},
year = {2018},
abstract = {The crystal chemistry of a cafarsite sample from the
fengitic orthogneisses of the Mt. Leone-Arbola nappe (Lower
Penninic), forming the central body of Mount Cervandone and
cropping out both in Switzerland and Italy (Alpe Devero
area, Verbano-Cusio-Ossola province), was investigated by
electron microprobe analysis in wavelength-dispersive mode
(EPMA-WDS), single-crystal Raman spectroscopy, and
single-crystal X-ray and neutron diffraction at 293 K. The
sample of cafarsite of this study was found experimentally
to be anhydrous and the chemical formula obtained on the
basis of the EPMA-WDS data and structural refinements is the
following: Ca1,Ca2 (Ca15.56Na0.44)Σ16 Fe1 (Na0.53Fe2+
0.17REE0.30)Σ1.00 Mn1,Ti,Fe2 (Ti7.46Fe3+ 4.47Fe2+ 3.20Mn2+
0.85Al0.11) Σ16.11 As1,As2,As3 (AsO3)28 F F, with the
general chemical formula Ca16(Na,Fe2+,REE)(Ti,
Fe3+,Fe2+,Mn2+,Al)16(AsO3)28F [or
Ca16(Na,Fe2+,REE)(Ti,Fe3+,Al)12(Fe2+,Mn)4(AsO3)28F]. Our
experimental findings show that fluorine, which was
unconsidered in the previous studies, is a key element. The
anhydrous nature of this sample is also confirmed by its
Raman spectrum, which does not show any evidence of active
bands ascribable to the O-H stretching region. The X-ray and
neutron structure refinements provide a structure model that
is partially in agreement with the previous experimental
findings. The space group (i.e. Pn3) and the unit-cell
constant [i.e. 15.9507(4) Å] are conform to the literature
data, but the structure of cafarsite, here refined, contains
the following building units: three independent AsO3 groups
(trigonal pyramids), one CaO6F polyhedron, one CaO8
polyhedron, two independent (Ti,Fe)O6 octahedra, one
(Na,Fe,REE)O8 polyhedron, and one (Mn,Fe)O6 octahedron.
Connections among polyhedra are mainly due to edge- or
vertex-sharing; the AsO3 groups are not connected to each
other.},
cin = {JCNS-FRM-II / JCNS-2 / MLZ},
ddc = {530},
cid = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
I:(DE-Juel1)JCNS-2-20110106 / I:(DE-588b)4597118-3},
pnm = {6G4 - Jülich Centre for Neutron Research (JCNS) (POF3-623)
/ 6G15 - FRM II / MLZ (POF3-6G15)},
pid = {G:(DE-HGF)POF3-6G4 / G:(DE-HGF)POF3-6G15},
experiment = {EXP:(DE-MLZ)HEIDI-20140101},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000445231600001},
doi = {10.1007/s00269-018-0964-z},
url = {https://juser.fz-juelich.de/record/859486},
}