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.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry