The Structure of High Pressure Ca(OD)2II from Powder Neutron Diffraction: Relationship to the ZrO2and EuI2Structures

Kurt Leinenweber, Dan E. Partin, Udo Schuelke, Michael O'Keeffe, Robert B. Von Dreele

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Abstract

The "unquenchable" high pressure form of Ca(OD)2[Ca(OH)2II] has been synthesized at 9 GPa and 400°C and recovered to ambient pressure at cryogenic temperatures. The structure was determined from powder neutron diffraction data using the Rietveld technique. The symmetry is monoclinicP21/cwitha=5.3979(4) Å,b=6.0931(4) Å,c=5.9852(4) Å,β=103.581(6)°,Z=4 at 1 atm and 11 K.Rwp=2.8%,Rp=1.9%, reducedχ2=6.6. for 117 variables. The calcium and oxygen substructure is intermediate between that inα-PbO2and that in fluorite; it was previously described as isostructural with baddeleyite (ZrO2), but it is more accurately described as isostructural with EuI2. This structure is distinguished by the presence of a 36anion net parallel to (100). Only one of the two kinds of D atoms in the structure shows appreciable hydrogen bonding to O, with a second neighbor D ... O distance of 1.91 Å, and an O-D ... O angle of 153.2°; the other D atom has 3 second-neighbor oxygens near 2.6 Å away.

Original languageEnglish (US)
Pages (from-to)267-273
Number of pages7
JournalJournal of Solid State Chemistry
Volume132
Issue number2
DOIs
StatePublished - Sep 1 1997

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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