<p> The crystal structure of k2SnBr6 has been reinvestigated using single crystal x-ray diffraction techniques. Three dimensional intensity data obtained photographically have been used to refine the structure, by the least square analysis. The structure is found to be slightly distorted from the regular cubic k2PtCl6 structure in a manner similar to K2TeBr6. The Sn-Br bond is found to be 2.601 A. </p> <p> The structure of k2SnBr6 is found to be monoclinic with space group P21/n and a = 7.435 ± 0.017 A, b= 7.437 ± 0.017 A, and c = 10.568 ± 0.006 A. </p> <p> A review of other crystals with similar structure is included in this thesis included the theory of x-ray diffraction and crystal structure as applicable to the present problem is discussed briefly. </p> / Thesis / Master of Science (MSc)

The crystal structure of metarossite, ideally CaV2O6 center dot 2H(2)O [chemical name: calcium divanadium(V) hexaoxide dihydrate], was first determined using precession photographs, with fixed isotropic displacement parameters and without locating the positions of the H atoms, leading to a reliability factor R = 0.11 [Kelsey & Barnes (1960). Can. Mineral. 6, 448- 466]. This communication reports a structure redetermination of this mineral on the basis of single- crystal X- ray diffraction data of a natural sample from the Blue Cap mine, San Juan County, Utah, USA (R1 = 0.036). Our study not only confirms the structural topology reported in the previous study, but also makes possible the refinement of all non- H atoms with anisotropic displacement parameters and all H atoms located. The metarossite structure is characterized by chains of edge- sharing [CaO8] polyhedra parallel to [100] that are themselves connected by chains of alternating [VO5] trigonal bipyramids parallel to [010]. The two H2O molecules are bonded to Ca. Analysis of the displacement parameters show that the [VO5] chains librate around [010]. In addition, we measured the Raman spectrum of metarossite and compared it with IR and Raman data previously reported. Moreover, heating of metarossite led to a loss of water, which results in a transformation to the brannerite- type structure, CaV2O6, implying a possible dehydration pathway for the compounds M2+V2O6 center dot xH(2)O, with M = Cu, Cd, Mg or Mn, and x = 2 or 4.