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@ARTICLE{Gatta:186695,
author = {Gatta, G. D. and Vignola, P. and Meven, Martin},
title = {{O}n the complex {H}-bonding network in paravauxite,
{F}e$^{2}$+{A}l$_{2}$({PO}$_{4}$)$_{2}$({OH})$_{2}$·8{H}$_{2}${O}:
{A} single-crystal neutron diffraction study},
journal = {Mineralogical magazine},
volume = {78},
number = {4},
issn = {0026-461X},
address = {Twickenham},
publisher = {Mineralogical Society of Great Britain and Ireland},
reportid = {FZJ-2015-00767},
pages = {841-850},
year = {2014},
abstract = {The crystal structure and the chemical composition of a
paravauxite from the Siglo Veinte Mine, Llallagua, Bustillo
Province, Potosi Department, Bolivia [Fe(Formula Formula
Mg0.064Ca0.002)Σ0.998Al(1)Al(2)Al2.005P(P1.998Si0.002)Σ2O8(OH)2·8H2O,
a = 5.242(1) Å, b = 10.569(2) Å, c = 6.970(2) Å, α =
106.78(3)°, β = 110.81(2)° and γ = 72.29(2)°, space
group P1İ], was investigated by single-crystal neutron
diffraction and electron microprobe analysis in
wavelength-dispersive mode. Neutron-intensity data were
collected at 293 K and anisotropic structure refinement was
performed. At the end of the refinement no peak larger than
1.3 fm/ Å3 was present in the final difference-Fourier map
of the nuclear density. The final statistical index was R1 =
0.0495 for 194 refined parameters and 1678 unique
reflections with Fo > 4σ(Fo). Eleven independent H sites
(i.e. H(1), H(2), H(3), H(4A), H(4B), H(5), H(6), H(7),
H(8), H(9A) and H(9B)), all at ~1 Å from the respective O
sites, were located successfully. H(4A) and H(4B) and H(9A)
and H(9B) are two mutually exclusive subsite couples only
0.4–0.6 Å apart. The complex H-bonding scheme in the
paravauxite structure is now well defined and 12 independent
H bonds, with an energetically favourable bonding
configuration, are described. A comparison between the
previous experimental findings based on Raman and infrared
spectroscopy and those obtained in this present study is
carried out. Paravauxite provides the rare opportunity to
investigate the H-bond configuration of coexisting hydroxyl
groups and H2O molecules in minerals by single-crystal
neutron diffraction. H2O is present as zeolitic (i.e. lying
in the cavities) and non-zeolitic H2O (i.e. bonded to Al or
Fe to form Al or Fe octahedra).},
cin = {JCNS (München) ; Jülich Centre for Neutron Science JCNS
(München) ; JCNS-FRM-II / JCNS-2 / PGI-4 / JARA-FIT},
ddc = {550},
cid = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
I:(DE-Juel1)JCNS-2-20110106 / I:(DE-Juel1)PGI-4-20110106 /
$I:(DE-82)080009_20140620$},
pnm = {54G - JCNS (POF2-54G24)},
pid = {G:(DE-HGF)POF2-54G24},
experiment = {EXP:(DE-MLZ)HEIDI-20140101},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000344420600004},
doi = {10.1180/minmag.2014.078.4.05},
url = {https://juser.fz-juelich.de/record/186695},
}