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@ARTICLE{Gatta:276652,
author = {Gatta, G. D. and Meven, Martin and Redhammer, Günther J.
and Vignola, Pietro and McIntire, Garry J.},
title = {{S}ingle-crystal neutron diffraction and {M}össbauer
spectroscopic study of hureaulite,
({M}n,{F}e)$_5$({PO}$_4$)$_2$({HPO}$_4$)$_2$({H}$_2${O})$_4$},
journal = {European journal of mineralogy},
volume = {27},
number = {6},
issn = {0935-1221},
address = {Alexandria, Va.},
publisher = {GeoScienceWorld},
reportid = {FZJ-2015-06980},
pages = {},
year = {2016},
abstract = {The crystal chemistry of hureaulite from the Jocão
(Cigana) pegmatite, Conselheiro Pena, Doce Valley, Minas
Gerais (Brazil), was investigated by electron microprobe
analysis in wavelength-dispersive mode, single-crystal Laue
(at 293 K) and monochromatic neutron diffraction (at 2.3 K),
and 57Fe-Mössbauer spectroscopy
[M(1),M(2),M(3)(Mn2+3.61Fe2+1.21Ca0.11Mg0.03)(sum=4.96)(P(2)PO4)2(H1.04P(1)PO4)2(H2O)3.92,
Z = 4, a = 17.603(6), b = 9.087(2), c = 9.404(4) Å, beta =
96.66(4) °, and V = 1494.1(9) Å3 at 293 K, space group
C2/c]. The neutron refinements confirm the general structure
model previously reported, showing that five independent H
sites (with full site occupancy) occur in the hureaulite
structure, one of them as member of the unique hydroxyl
group (i.e., O(1)-H(1)) and the other four belonging to two
independent H2O molecules (i.e., H(2)-O(9)-H(3) and
H(4)-O(10)-H(5)). The hydroxyl group is the vertex of one of
the two independent P-tetrahedra (i.e., HOPO3), whereas the
two H2O molecules are the vertices of the (Mn,Fe)-octahedra.
No zeolitic H2O occurs in hureaulite structure. The complex
hydrogen bonding scheme in hureaulite is now well defined,
with five hydrogen bonds energetically favorable. The
elements distribution among the octahedral sites, deduced on
the basis of the neutron structure refinements, shows that
the highest fraction of Fe populates the M(2) site
$(~36\%),$ whereas lower fractions are observed at M(1) and
M(3) (i.e., ~13-15 and $~11-12\%,$ respectively). The 57Fe
Mössbauer spectrum of hureaulite confirms the absence of
ferric iron in the sample. The spectrum shows four well
separated absorption lines which are better fitted with
three doublets. The well resolved doublet (with the largest
quadrupole splitting) is here assigned to the M(3) site, in
line with the pronounced preference of Mn2+ for the M(3)
site as obtained by the neutron structure refinements. The
two innermost doublets have almost identical isomer shifts,
though with slightly different quadrupole splitting values;
the smaller quadrupole splitting value is assigned to the
M(2) site, which is expected to have a slightly lower
polyhedral distortions than the M(1) site, according to the
experimental findings based on the neutron refinements.},
cin = {JCNS-FRM-II / JCNS-2},
ddc = {550},
cid = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
I:(DE-Juel1)JCNS-2-20110106},
pnm = {6G15 - FRM II / MLZ (POF3-6G15) / 6G4 - Jülich Centre for
Neutron Research (JCNS) (POF3-623)},
pid = {G:(DE-HGF)POF3-6G15 / G:(DE-HGF)POF3-6G4},
experiment = {EXP:(DE-MLZ)HEIDI-20140101},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000372068500011},
doi = {10.1127/ejm/2015/0027-2464},
url = {https://juser.fz-juelich.de/record/276652},
}