Structure of high pressure Ca(OD){sub 2} II from powder neutron diffraction: Relationship to the ZrO{sub 2} and EuI{sub 2} structures
Journal Article
·
· Journal of Solid State Chemistry
- Arziona State Univ., Tempe, AZ (United States); and others
The {open_quotes}unquenchable{close_quotes} high pressure form of Ca(OD){sub 2} [Ca(OH){sub 2}II] has been synthesized at 9 GPa and 400{degrees}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 monoclinic P2{sub 1}/c with a = 5.3979(4) {angstrom}, b = 6.0931(4) {angstrom}, c = 5.9852(4) {angstrom}, {beta} = 103.581(6), Z = 4 at 1 atm and 11 K. R{sub wp} = 2.8%, R{sub p} = 1.9%, reduced {chi}{sup 2} = 6.6. for 117 variables. The calcium and oxygen substructure is intermediate between that in {alpha}-PbO{sub 2} and that in fluorite; it was previously described as isostructural with baddeleyite (ZrO{sub 2}), but it is more accurately described as isostructural with EuI{sub 2}. This structure is distinguished by the presence of a 3{sup 6} anion met 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 {angstrom}, and an O-D...O angle of 153.2{degrees}; the other D atom has 3 second-neighbor oxygens near 2.6 {angstrom} away.
- OSTI ID:
- 569682
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 2 Vol. 132; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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