Anti-KSbF6 structure of CaTbF6 and CdTbF6: a confirmation of the singular crystal chemistry of Tb4+ in fluorides.
The crystal structures of two new tetravalent terbium fluorides, CaTbF6 and CdTbF6, have been determined from X-ray and neutron powder diffraction data. The title compounds exhibit an anti-KSbF6 structure, the three-dimensional framework of which is built of [TbF6]2- chains of edge-sharing dodecahedra further linked, by sharing corners, to isolated [MF6]4- octahedra (M=Ca, Cd). The mechanism of the anionic sublattice rearrangement when going from KSbF6 to CaTbF6 is described and related to a simple cubic fluoride-ion packing. Comparison with the crystal structures of beta-BaTbF6 and other representatives of the M(II)M('IV)F6 family allows the singular crystal-chemical properties of some fluoroterbates to be emphasized.
Josse
Michaël
M
Université Blaise Pascal, Laboratoire des Matériaux Inorganiques, UMR 6002 CNRS, 24 Avenue des Landais, 63177 Aubiere, France.
Dubois
Marc
M
El-Ghozzi
Malika
M
Cellier
Joël
J
Avignant
Daniel
D
D002104:Cadmium / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D003460:Crystallization; D018360:Crystallography, X-Ray; D005459:Fluorides / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D033363:Neutron Diffraction; D011188:Potassium / Q000737:chemistry*; D013725:Terbium / Q000737:chemistry*
D002104:Cadmium; D013725:Terbium; D005459:Fluorides; D011188:Potassium; D002118:Calcium