% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@ARTICLE{Murphy:848119,
      author       = {Murphy, Gabriel L. and Wang, Chun-Hai and Beridze, George
                      and Zhang, Zhaoming and Kimpton, Justin A. and Avdeev, Maxim
                      and Kowalski, Piotr and Kennedy, Brendan J.},
      title        = {{U}nexpected {C}rystallographic {P}hase {T}ransformation in
                      {N}onstoichiometric {S}r{UO} 4– x : {R}eversible {O}xygen
                      {D}efect {O}rdering and {S}ymmetry {L}owering with
                      {I}ncreasing {T}emperature},
      journal      = {Inorganic chemistry},
      volume       = {57},
      number       = {10},
      issn         = {1520-510X},
      address      = {Washington, DC},
      publisher    = {American Chemical Society},
      reportid     = {FZJ-2018-03395},
      pages        = {5948 - 5958},
      year         = {2018},
      abstract     = {In situ synchrotron powder X-ray diffraction measurements
                      have demonstrated that SrUO4 undergoes a reversible phase
                      transformation under reducing conditions at high
                      temperatures, associated with the ordering of oxygen defects
                      resulting in a lowering of crystallographic symmetry. When
                      substoichiometric rhombohedral α-SrUO4–x, in space group
                      R3̅m with disordered in-plane oxygen defects, is heated
                      above 200 °C in a hydrogen atmosphere it undergoes a first
                      order phase transformation to a (disordered) triclinic
                      polymorph, δ-SrUO4–x, in space group P1̅. Continued
                      heating to above 450 °C results in the appearance of
                      superlattice reflections, due to oxygen-vacancy ordering
                      forming an ordered structure δ-SrUO4–x. Cooling
                      δ-SrUO4–x toward room temperature results in the
                      reformation of the rhombohedral phase α-SrUO4–x with
                      disordered defects, confirming the reversibility of the
                      transformation. This suggests that the transformation,
                      resulting from oxygen vacancy ordering, is not a consequence
                      of sample reduction or decomposition, but rather represents
                      a change in the energetics of the system. A strong reducing
                      atmosphere is required to generate a critical amount of
                      oxygen defects in α-SrUO4–x to enable the transformation
                      to δ-SrUO4–x but once formed the transformation between
                      these two phases can be induced by thermal cycling. The
                      structure of δ-SrUO4–x at 1000 °C was determined using
                      symmetry representation analysis, with the additional
                      reflections indexed to a commensurate distortion vector k =
                      ⟨1/4 1/4 3/4⟩. The ordered 2D layered triclinic
                      structure of δ-SrUO4–x can be considered a structural
                      distortion of the disordered 2D layered rhombohedral
                      α-SrUO4–x structure through the preferential
                      rearrangement of the in-plane oxygen vacancies. Ab initio
                      calculations using density functional theory with
                      self-consistently derived Hubbard U parameter support the
                      assigned ordered defect superstructure model. Entropy
                      changes associated with the temperature dependent
                      short-range ordering of the reduced U species are believed
                      to be important and these are discussed with respect to the
                      results of the ab initio calculations.},
      cin          = {IEK-6 / JARA-HPC},
      ddc          = {540},
      cid          = {I:(DE-Juel1)IEK-6-20101013 / $I:(DE-82)080012_20140620$},
      pnm          = {161 - Nuclear Waste Management (POF3-161) / Atomistic
                      modeling of radionuclide-bearing materials for safe
                      management of high level nuclear waste.
                      $(jara0037_20181101)$ / Investigation of the new materials
                      for safe management of high level nuclear waste.
                      $(jara0038_20121101)$},
      pid          = {G:(DE-HGF)POF3-161 / $G:(DE-Juel1)jara0037_20181101$ /
                      $G:(DE-Juel1)jara0038_20121101$},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:29714481},
      UT           = {WOS:000433013600026},
      doi          = {10.1021/acs.inorgchem.8b00463},
      url          = {https://juser.fz-juelich.de/record/848119},
}