Gagarinite structure

Gagarinite structure, 846 Galactose oxidase, 700 copper, 655 Galena brines, 853 depression, 783 dissolution, 787 humic acids, 861 Gallium isotopes... 

Gagarinite, NaCaLnF6, apparently contains isolated LnF63- octahedra, but its crystal structure is unknown. Hexachloromanganate(II) and ferrate(II) ions are present in the minerals chlor-manganokalite and rinneite, respectively, and iron(II) or iron(III) ions with four and five chloride ions in the coordination sphere are represented by the species douglasite and erythrosiderite. The coordination spheres are completed by water molecules, and these chloro complexes correspond to well-known compounds prepared in the laboratory.2... 

Iodides of this class of compounds are not known. On the other hand, a fluoride with the idealized composition NaCaYF and the same structure even occurs in nature as the mineral gagarinite (Hughes and Drexler 1994). 

Class 5 structures without anionic groups - fluorides and simple oxides FLUOCERITE-(Cc) (=tysonite), CeFj FLUOCERlTE-(La), LaFj GAGARINITE-(Y), (Y,Ca)2(Na,D)F6 TVEITITE-(Y), Cai4Y5p43... 

The crystal structure of gagarinite-(Y) (fig. 90) consists of nine-coordinated (R,Ca) polyhedra and partially occupied Na sites with octahedral coordination (Voronkov et al. 1962). This structure may be considered as derived from that of UCI3 the symmetry changes from P63/m (UCI3) to P3 [gagarinite-(Y)]. The Na atoms are the extra ones they have flattened octahedra as their coordination polyhedra, and these lie alternately with empty polyhedra of the same shape on the three-fold axes along... 

Tricapped trigonal prisms (m) are frequently found in the nine-coordinated rare earth sites. A typical example is the YOe(OH)3 polyhedron in agardite-(Y). This type of polyhedron is also found in the structures of belovite-(Ce), frangoisite-(Nd) and gagarinite-(Y). The crystal structure of tveitite-(Y) contains monocapped square antiprisms (1), and that of sahamalite-(Ce) contains monocapped cubes (k). 

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