Annular dynamical disorder of the rare earth ions in a La2Zr2O7 pyrochlore via single crystal synchrotron X-ray diffraction
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Y. Tabira
Abstract
The reciprocal lattices of a range of rare earth titanate and zirconate pyrochlores have recently been shown to exhibit an extremely characteristic diffuse intensity distribution identical in form to that characteristic of β-cristobalite implying the existence of β-cristobalite-like orientational disorder of essentially rigid, (O2)(R3+)4 tetrahedra within the pyrochlore structure type. A single crystal X-ray diffraction study of La2Zr2O7 has been carried out utilizing synchrotron radiation in order to investigate this proposed orientational disorder and to determine an unknown oxygen atom fractional co-ordinate. An annular distribution of residual electron density is found around the average La ion positions in {111} planes perpendicular to the local O2–La–O2 directions and interpreted as implying that the La ions never in fact occupy the average 16d positions but rather are dynamically disordered around an annulus perpendicular to that direction in an exactly analogous manner to that which occurs in β-cristobalite.
© 2001 Oldenbourg Wissenschaftsverlag GmbH
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Articles in the same Issue
- Calculation of the elastic constants of the Al2SiO5 polymorphs andalusite, sillimanite and kyanite
- Charge density studies utilizing powder diffraction and MEM. Exploring of high Tc superconductors, C60 superconductors and manganites
- A note on mean distances, R̅[MO₆], in substituted polyhedra, [(M1-xMx′)O6], in the crystal structures of oxygen based solid solutions: local versus crystal averaging methods
- Annular dynamical disorder of the rare earth ions in a La2Zr2O7 pyrochlore via single crystal synchrotron X-ray diffraction
- Prediction of hydrogen positions in complex structures
- Thermal induced transformations on completely Zn2+ exchanged zeolites A and Y
- Molecular structure of 1-(2,4,6-tri-tert-butylphenyl)-4,4-bis(dimethylamino)-1-aza-2,3λ3-phosphabutadiene-1,3
- Crystal structure of the complex of 1,8-bis(dimethylamino)naphthalene with p-nitrosophenol by powder diffraction methods
- Crystal and molecular structure of 5-carboxy-2-thiouracil monohydrate
- Book Review
