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@ARTICLE{Jalarvo:188359,
      author       = {Jalarvo, Niina and Gourdon, Olivier and Ehlers, Georg and
                      Tyagi, Madhusudan and Kumar, Sanat K. and Dobbs, Kerwin D.
                      and Smalley, Robert J. and Guise, William E. and
                      Ramirez-Cuesta, Anibal and Wildgruber, Christoph and
                      Crawford, Michael K.},
      title        = {{S}tructure and {D}ynamics of {O}ctamethyl-{POSS}
                      {N}anoparticles},
      journal      = {The journal of physical chemistry / C},
      volume       = {118},
      number       = {10},
      issn         = {1932-7455},
      address      = {Washington, DC},
      publisher    = {Soc.},
      reportid     = {FZJ-2015-01765},
      pages        = {5579 - 5592},
      year         = {2014},
      abstract     = {Polyoligosilsesquioxanes (POSS) are a large family of
                      Si–O cage molecules that have diameters of 1–2 nm and
                      can be viewed as perfectly monodisperse silica
                      nanoparticles. POSS can be synthesized with a wide variety
                      of functional ligands attached to their surfaces. Here we
                      report the results of a comprehensive study of the crystal
                      structure and ligand dynamics of one of the simplest POSS
                      nanoparticles, octamethyl-POSS or Si8O12(CH3)8, where the
                      central Si8O12 cage is surrounded by eight methyl ligands.
                      Neutron powder diffraction data highlight the presence of
                      strongly temperature-dependent methyl group rotational
                      dynamics. Vibrational spectra were measured using Raman and
                      inelastic neutron scattering techniques, and the results of
                      the measurements were compared with the predictions of
                      density functional theory calculations. In particular, the
                      inelastic neutron scattering spectra show the fundamental
                      and first overtone transitions of the methyl torsional
                      vibrations; these transitions are forbidden in both Raman
                      and infrared spectroscopy for the molecule with its ideal
                      octahedral symmetry. The energies of these transitions are
                      used to determine the height of the torsional energy
                      barrier. Direct measurements of the methyl group dynamics
                      using quasielastic incoherent neutron scattering provide the
                      hydrogen atom jump distance and the activation energy for
                      rotation of the methyl groups. Together these results
                      provide a detailed picture of the structure and ligand
                      dynamics of this POSS molecule.},
      cin          = {Neutronenstreuung ; JCNS-1 / JCNS-SNS},
      ddc          = {540},
      cid          = {I:(DE-Juel1)JCNS-1-20110106 /
                      I:(DE-Juel1)JCNS-SNS-20110128},
      pnm          = {54G - JCNS (POF2-54G24) / 451 - Soft Matter Composites
                      (POF2-451)},
      pid          = {G:(DE-HGF)POF2-54G24 / G:(DE-HGF)POF2-451},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000333005700059},
      doi          = {10.1021/jp412228r},
      url          = {https://juser.fz-juelich.de/record/188359},
}