Crystal structures of various organic materials and a statistical analysis of single crystal X -ray diffraction data from potassium -doped barium plumbate

A general explanation of the collection and reduction of crystallographic data is presented. This is followed by a brief explanation of routine crystal structure solution and refinement. The results of five routine organic structure solutions are included. A discussion of the perovskite structure aristotype is followed by an elaboration of four common distortions to the aristotype that result in perovskite hettotypes. A crystal structure for barium bismuthate is analyzed to explain its occurrence as a perovskite aristotype. A literature review of powder and neutron diffraction structures reported for barium plumbate included a wide variety of perovskite hettotypes and one aristotype. No reports of a structure resulting from single crystal X-ray diffraction data were found in the literature. Single crystal X-ray diffraction data were collected for two samples of barium plumbate at the LSU X-ray Crystallography Laboratory. The data were reduced using Enraf Nonius' Structure Determination Package, and a structure was refined using Direct Methods and MoLEN. Both crystals exhibited pseudo cubic symmetry and defied routine structure solution. They possessed the lattice constants of a cube (a = 4.27 A), but apparently not the full set of symmetry elements of a cube. Thus, the crystals could not be conclusively assigned to a space group using routine methods. An in-depth statistical analysis commenced for the intensity data of Crystal 2. Application of the methods of cluster analysis and the analysis of variance resulted in the declaration of a structure which, at the 95% confidence level, is consistent with the symmetry of space group number 221 - Pm3m, the space group of the perovskite aristotype.