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@ARTICLE{Blanchard:19977,
      author       = {Blanchard, D. and Maronsson, J.B. and Riktor, M.D. and
                      Kheres, J. and Sveinbjörnsson, D. and Bardají, E.G. and
                      Léon, A. and Juranyi, F. and Wuttke, J. and Lefmann, K. and
                      Hauback, B.C. and Fichtner, M. and Vegge, T.},
      title        = {{H}indered {R}otational {E}nergy {B}arriers of {BH}4-
                      {T}etrahedra in ß-{M}g ({BH}4)2 from {Q}uasielastic
                      {N}eutron {S}cattering and {DFT} {C}alculations},
      journal      = {The journal of physical chemistry / C},
      volume       = {116},
      issn         = {1932-7447},
      address      = {Washington, DC},
      publisher    = {Soc.},
      reportid     = {PreJuSER-19977},
      pages        = {2013 - 2023},
      year         = {2012},
      note         = {This work is based on experiments performed at the Swiss
                      spallation neutron source SINQ, Paul Scherrer Institute,
                      Villigen, Switzerland, and at FRMII, JCNS Garching, Germany.
                      It has been supported by the Danish Council for independent
                      Research through DANSCATT. The authors acknowledge the
                      European Graduate School for Sustainable Energy Technology
                      and the Nordic Center for Excellence on Hydrogen Storage
                      Materials. The Danish Center for Scientific Computing is
                      acknowledged for supercomputer access. The Center for Atomic
                      Materials Design (CAMD) is supported by the Lundbeck
                      Fondation. Financial support by EU-IP NESSHY (contract
                      #518271) and the ERA-NET project "Hy-CO" is also gratefully
                      acknowledged.},
      abstract     = {In this work, hindered rotations of the BH4- tetrahedra in
                      Mg(BH4)(2) were studied by quasielastic neutron scattering,
                      using two instruments with different energy resolution, in
                      combination with density functional theory (DFT)
                      calculations. Two thermally activated reorientations of the
                      BH4- units, around the 2-fold (C-2) and 3-fold (C-3) axes
                      were observed at temperatures from 120 to 440 K. The
                      experimentally obtained activation energies (E-aC2 = 39 and
                      76 meV and E-aC3 = 214 meV) and mean residence times between
                      reorientational jumps are comparable with the energy
                      barriers obtained from DFT calculations. A linear dependency
                      of the energy barriers for rotations around the C-2 axis
                      parallel to the Mg-Mg axis with the distance between these
                      two axes was revealed by the DFT calculations. At the lowest
                      temperature (120 K) only $15\%$ of the BH4- units undergo
                      rotational motion and from comparison with DFT results it is
                      expectedly the BH4- units with the boron atom closest to the
                      Mg-Mg axis, although dynamics related to local disorder
                      existing at the boundary of the antiphase domains or to the
                      presence of solvent in the sample cannot be strictly
                      excluded. No long-range diffusion events were observed.},
      keywords     = {J (WoSType)},
      cin          = {ICS-1 / JCNS (München) ; Jülich Centre for Neutron
                      Science JCNS (München) ; JCNS-FRM-II / JCNS-1},
      ddc          = {540},
      cid          = {I:(DE-Juel1)ICS-1-20110106 /
                      I:(DE-Juel1)JCNS-FRM-II-20110218 /
                      I:(DE-Juel1)JCNS-1-20110106},
      pnm          = {BioSoft: Makromolekulare Systeme und biologische
                      Informationsverarbeitung / Großgeräte für die Forschung
                      mit Photonen, Neutronen und Ionen (PNI)},
      pid          = {G:(DE-Juel1)FUEK505 / G:(DE-Juel1)FUEK415},
      experiment   = {EXP:(DE-MLZ)SPHERES-20140101},
      shelfmark    = {Chemistry, Physical / Nanoscience $\&$ Nanotechnology /
                      Materials Science, Multidisciplinary},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000299584800045},
      doi          = {10.1021/jp208670v},
      url          = {https://juser.fz-juelich.de/record/19977},
}