Acta Cryst. (2007). E63, i203-i204  [ doi:10.1107/S1600536807060436 ]

KCaNb₂O₆F from a combined synchrotron X-ray and neutron powder diffraction study

C.-Y. Yoo and S.-J. Kim

Abstract: Potassium calcium diniobium hexaoxide fluoride, KCaNb₂O₆F, crystallizes in the cubic pyrochlore-type structure. In the crystal structure, NbO₆ octahedra are linked together by common corners to form a three-dimensional [Nb₂O₆]^2- network. (K,Ca) and F atoms, which are located in the voids of the [Nb₂O₆]^2- network, form zigzag [(K,Ca)F]²⁺ chains. The K and Ca atoms are distributed statistically over the same crystallographic position (site-occupancy factor = 0.5), having an eightfold coordination by six O atoms from the NbO₆ octahedra and by two F atoms. All atoms lie on special positions, viz. Nb has m, the (K,Ca) site has m, O has 2mm and F has 3m site symmetry.

Online 28 November 2007

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