The crystal structure of α-KTh6F25, a polymorph of CsU6F25

Abstract

Crystals of ~-KTh6F2 s are hexagonal-rhombohedral, R3m, with hexagonal axes a0= 8.313 (2), Co = 25.262 (4)/~, Z= 3 and o(cal)= 6.281 g.cm-3. Structural units of ~-KTh6F25 are identical to those of CsU6F2s and comprise two adjacent rings of Tha+-F polyhedra, 6 polyhedra per ring, with an alkali metal ion centered between the rings. The structural units are stacked ABCABC along Co in ~-KTh6F25 and ABAB in CsU6F25. K-F distances are 3.19 (2) and 3.20 (3)/~. Th-F distances range from 2.308 (1) to 2.541 (9) ,~.

The Crystal Structures of CsTh6F25 and NaTh3F13

“…Similar phases of 1, RbTh 6 F 25 and KTh 6 F 25 , were proposed to crystallize in P6 3 /mmc via powder diffraction data [8]. However, the only single crystal data available for this phase of alkali thorium fluoride is for a-KTh 6 F 25 , a polymorph that was found to crystallize in R-3m [16]. Although it forms a framework system that contains pores, its thorium polyhedra stack in an ABCABC order, as compared to our structure that stacks in an ABAB order, similar to CsU 6 F 25 .…”

Hydrothermal Descriptive Chemistry and Single Crystal Structure Determination of Cesium and Rubidium Thorium Fluorides

“…Previous work was done primarily in molten alkali fluoride salts and led to a variety of alkali metal thorium fluorides in the tetravalent state. A considerable number of A x Th y F z compounds were characterized, mostly by either powder or single crystal diffraction. ,− Most of these phases are sodium and potassium thorium fluorides with, to our knowledge, only one rubidium thorium fluoride and no cesium-containing examples previously reported as single crystal structures.…”

Immobilization of Alkali Metal Fluorides via Recrystallization in a Cationic Lamellar Material, [Th(MoO4)(H2O)4Cl]Cl·H2O

“…The PXRD patterns of the AF-soaked samples were compared with the theoretical patterns of all published alkali thorium fluoride compounds in the inorganic crystal structure database (ICSD), within which K 7 Th 6 F 31 (ICSD-2711) has a good agreement with the KF-soaked TMC sample. 35 The PXRD patterns of NaF-and CsF-soaked TMC samples do not agree with any published sodium and potassium thorium fluorides, respectively, suggesting that they are either new complexes or mixtures of multiple fluoride species. The phase difference between NaF-, KF-, and CsF-soaked TMC products could be attributed to the variety of ionic radii of the alkali metals, which influence the overall packing of the crystal structures.…”

“…The experimental PXRD pattern of TMC is consistent with the calculated one and is obviously different from those of TMC samples after being immersed in 0.1 M AF (A = Na, K, and Cs) solutions. The PXRD patterns of the AF-soaked samples were compared with the theoretical patterns of all published alkali thorium fluoride compounds in the inorganic crystal structure database (ICSD), within which K 7 Th 6 F 31 (ICSD-2711) has a good agreement with the KF-soaked TMC sample . The PXRD patterns of NaF- and CsF-soaked TMC samples do not agree with any published sodium and potassium thorium fluorides, respectively, suggesting that they are either new complexes or mixtures of multiple fluoride species.…”