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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},
}