Crystal structures and stability of K2ThF6 and K7Th6F31 on compression

K2ThF6 and K7Th6F31 were prepared hydrothermally as single crystals. Their structures were investigated with single-crystal X-ray diffraction at ambient conditions and at high pressures using diamond anvil cells. The results of this study indicate that the two materials, with chains of face-sharing tricapped trigonal prisms ThF9 and with layers of square antiprisms ThF8 sharing their edges in Th2F14 doublets, respectively, are structurally stable at least to about 9 GPa at room temperature. This observation suggests that, in general, moderate high pressure has no effect on the coordination polyhedra around the Th atoms and the topology of the structure of complex thorium fluorides. The bulk compressibility of the thorium fluorides entirely depends on the alkali metal present in the structure.