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@ARTICLE{Murphy:856927,
      author       = {Murphy, Gabriel and Kegler, Philip and Zhang, Yingjie and
                      Zhang, Zhaoming and Alekseev, Evgeny and de Jonge, Martin D.
                      and Kennedy, Brendan J.},
      title        = {{H}igh-{P}ressure {S}ynthesis, {S}tructural, and
                      {S}pectroscopic {S}tudies of the {N}i–{U}–{O} {S}ystem},
      journal      = {Inorganic chemistry},
      volume       = {57},
      number       = {21},
      issn         = {1520-510X},
      address      = {Washington, DC},
      publisher    = {American Chemical Society},
      reportid     = {FZJ-2018-06254},
      pages        = {13847 - 13858},
      year         = {2018},
      abstract     = {The first comprehensive structural study of the Ni–U–O
                      system is reported. Single crystals of α-NiUO4, β-NiUO4,
                      and NiU3O10 were synthesized, and their structures were
                      refined—using synchrotron single-crystal X-ray diffraction
                      data supported by X-ray absorption spectroscopic
                      measurements. α-NiUO4 adopts an orthorhombic structure in
                      space group Pbcn and is isostructural to CrUO4 containing
                      corrugated two-dimensional (2D) layers of corner-sharing UO6
                      polyhedra and edge-sharing one-dimensional (1D) zigzag
                      α-PbO2 rutile-like chains of NiO6 polyhedra in the [001]
                      direction. β-NiUO4 is isostructural to MgUO4 and has an
                      orthorhombic structure in space group Ibmm, which contains
                      alternating 1D chains of edge-sharing UO6 and NiO6 polyhedra
                      in the [001] direction as in regular TiO2 rutile. NiU3O10
                      forms a triclinic structure in space group P1̅ and is
                      isostructural with CuU3O10, where it forms a
                      three-dimensional (3D) framework structure built through a
                      mixture of UO6 and UO7 polyhedra in which the NiO6 polyhedra
                      sit isolated within the framework. X-ray absorption
                      near-edge structure (XANES) measurements, conducted using
                      XANES mapping of single crystals, support the presence of
                      hexavalent uranium in the three structures. The polymorphs
                      of NiUO4 were found to only form under high-pressure and
                      high-temperature conditions (≥4 GPa and 700 °C). It is
                      argued that this is a consequence of the relative size
                      difference between the Ni2+ and U6+ cations, where the Ni2+
                      cation is effectively too small for the Ibmm structure and
                      too large for the Pbcn structure to form under ambient
                      pressure conditions. This does not appear to be an issue for
                      NiU3O10, which forms under ambient pressure conditions,
                      where NiO6 polyhedra sit isolated within the framework of 3D
                      connected UO6/UO7 polyhedra. Synthesis conditions indicate
                      that β-NiUO4 is the preferred higher-pressure phase and
                      that the transformation to this occurs irreversibly at a
                      temperature between 950 and 1000 °C, when P = 4 GPa. The
                      routes toward the synthesis of the oxides and the associated
                      structural and spectroscopic results are described with
                      respect to the structural chemistry of the Ni–U–O
                      system, the larger AUO4 family of oxides (A = divalent or
                      trivalent cation), and also their relation to the
                      rutile-related family of oxides.},
      cin          = {IEK-6},
      ddc          = {540},
      cid          = {I:(DE-Juel1)IEK-6-20101013},
      pnm          = {161 - Nuclear Waste Management (POF3-161) / Helmholtz Young
                      Investigators Group: Energy (HGF-YIG-Energy)},
      pid          = {G:(DE-HGF)POF3-161 / G:(DE-HGF)HGF-YIG-Energy},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:30354086},
      UT           = {WOS:000449576900083},
      doi          = {10.1021/acs.inorgchem.8b02355},
      url          = {https://juser.fz-juelich.de/record/856927},
}