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@ARTICLE{Gatta:57967,
      author       = {Gatta, G. D. and Nestola, F. and Bromiley, G. D. and
                      Mattauch, S.},
      title        = {{T}he real topological configuration of the extra-framework
                      content in alkali-poor beryl: a multi methodological study},
      journal      = {American mineralogist},
      volume       = {91},
      issn         = {1945-3027},
      address      = {Washington, DC},
      publisher    = {Soc.},
      reportid     = {PreJuSER-57967},
      pages        = {29 - 34},
      year         = {2006},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {The crystal structure of alkali/water-poor beryl (1120 +
                      Na2O + Cs2O < 1.2 $wt\%)$ was reinvestigated by means of
                      laser ablation inductively coupled plasma mass spectroscopy,
                      thermogravimetric analysis, neutron diffraction, and
                      polarized infrared spectroscopy to determine the real
                      topological configuration of the extra-framework content in
                      the six-membered ring channels. Analysis of the nuclear
                      density Fourier map suggests that the (water) oxygen is
                      located along the sixfold axis at the 2a site (0,0, 1/4),
                      whereas the (water) protons are at -0.028(7), -0.071(3),
                      0.332(1). The hydrogen atoms are distributed in 6 x 2
                      equivalent positions, above and below the oxygen site.
                      Geometrical configuration of the water molecule is well
                      defined: the O-H bond distance is 0.949(18) angstrom and the
                      H-O-H bond angle is 106.9(2.2)degrees. The (HH)-H-... vector
                      is oriented at similar to 4 degrees from [001]. This
                      configuration is completely different from that found in
                      alkali-rich beryl, where the (HH)-H-... vector is
                      perpendicular to [00 1]. Na is probably located, with the
                      H2O oxygen, at the 2a site. According to the chemical
                      analysis, which shows that the amounts of other alkali and
                      earth-alkali cations are negligible (Rb, K, Mg, Mn <= 110
                      ppm, Ca <= 225 ppm, Cs <= 430 ppm), no effect of other
                      cations on the extra-framework population was observed in
                      the structural refinement. The final agreement index (R-1)
                      of the structural refinement was 0.037 for 34 refined
                      parameters and 160 unique reflections with F-0 > 4
                      sigma(F-0). The topological configuration of the H2O
                      molecule into the channel is confirmed by the spectroscopic
                      investigation. Polarized single-crystal IR spectra show that
                      the H2O molecule is oriented with the molecular symmetry
                      axis perpendicular to the hexagonal axis and (HH)-H-...
                      vector parallel (or quasi-parallel) to [001].},
      keywords     = {J (WoSType)},
      cin          = {Jülich Centre for Neutron Science JCNS (JCNS) ; JCNS /
                      IFF-ISM},
      ddc          = {550},
      cid          = {I:(DE-Juel1)JCNS-20121112 / I:(DE-Juel1)VDB342},
      pnm          = {Kondensierte Materie},
      pid          = {G:(DE-Juel1)FUEK414},
      shelfmark    = {Geochemistry $\&$ Geophysics / Mineralogy},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000234527900004},
      doi          = {10.2138/am.2006.1896},
      url          = {https://juser.fz-juelich.de/record/57967},
}