Crystal structure of I III IV Se4 compounds

Polycrystalline samples are produced for 13 different compounds of the form I III IV vacant Se4 where I is Cu, Ag, III is Al, Ga, In, and IV is Si, Ge, Sn. Debye-Scherrer powder photographs are taken for each compound and all found to have tetragonal symmetry. The ordering lines are analyzed and it is found that all of the compounds have the same structure. Intensity ratios for the 103:112 and 211:220 lines are determined and compared with predicted values for various ordered arrangements. It is found that the compounds have the chalcopyrite structure with the lattice vacancy and the group I atom arranged at random on one cation sublattice and the group III and group IV atoms at random on the other, i.e. (I vacant) (III IV) Se4. (author)