title: K(3)TaF(8) from laboratory X-ray powder data.
abstract: The crystal structure of tripotassium octafluoridotantalate, K(3)TaF(8), determined from laboratory powder diffraction data by the simulated annealing method and refined by total energy minimization in the solid state, is built from discrete potassium cations, fluoride anions and monocapped trigonal-prismatic [TaF(7)](2-) ions. All six atoms in the asymmetric unit are in special positions of the P6(3)mc space group: the Ta and one F atom in the 2b (3m) sites, the K and two F atoms in the 6c (m) sites, and one F atom in the 2a (3m) site. The structure consists of face-sharing K(6) octahedra with a fluoride anion at the center of each octahedron, forming chains of composition [FK(3)](2+) running along [001] with isolated [TaF(7)](2-) trigonal prisms in between. The structure of the title compound is different from the reported structure of Na(3)TaF(8) and represents a new structure type.
authors.affiliation: Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-845 36 Bratislava, Slovak Republic. lubomir.smrcok@savba.sk
authors.forename: Lubomír
authors.initials: L
authors.lastname: Smrcok
authors.forename: Radovan
authors.initials: R
authors.lastname: Cerný
authors.forename: Miroslav
authors.initials: M
authors.lastname: Boca
authors.forename: Iveta
authors.initials: I
authors.lastname: Macková
authors.forename: Blanka
authors.initials: B
authors.lastname: Kubíková