• DOI:10.2138/am-1995-5-605
• Corpus ID: 196903109

H in rutile-type compounds: I. Single-crystal neutron and X-ray diffraction study of H in rutile

@article{Swope1995HIR,
  title={H in rutile-type compounds: I. Single-crystal neutron and X-ray diffraction study of H in rutile},
  author={R. Jeffrey Swope and Joseph R. Smyth and Allen C. Larson},
  journal={American Mineralogist},
  year={1995},
  volume={80},
  pages={448 - 453}
}

• R. Swope, J. Smyth, A. Larson
• Published 1995
• Chemistry
• American Mineralogist

Abstract The crystal structure of natural hydrous rutile from a mantle eclogite nodule has been refined from single-crystal neutron diffraction data collected at 24 K. The chemical composition was 95.52 wt% TiO2, 0.74 wt% Fe2O3, 0.68 wt% Al2O3, 1.16 wt% Cr2O3, 1.86 wt% Nb2O5, and 0.04 wt% MnO, with approximately 13000 ppm OH-, as estimated by IR spectroscopy. The position of the H atom was located by examining the negative residuals in the difference Fourier maps. The refined position is near the shared edge of the cation octahedron at x|a = 0.42(1), y|b = 0.50(1), and z|c = 0 with a site occupancy of 2.7%, which is consistent with the H concentration estimated by IR spectroscopy. The O-H bond distance is 1.05 Å and the OH vector is in the (001) plane, which is consistent with the strong ω-polarization of the OH absorption observed in the IR spectra. Single-crystal X-ray data were collected from a synthetic anhydrous rutile crystal and a hydrous rutile crystal from the same mantle nodule as the sample used in the neutron study. The detailed X-ray structures of both rutiles were compared and no significant differences were found; the a|c ratios and the O position were identical within error. Therefore, we conclude that the addition of H into rutile for the purpose of charge-balancing excess 3 + cations does not significantly change the structure.