Mechanochemical synthesis and structural characterization of the I2-II-IV-VI4 quaternary chalcogenide Ag2CdGeSe4

Ag2CdGeSe4 – a I2-II-IV-VI4 quaternary chalcogenide – was synthesized by a mechanochemical synthesis route with a subsequent annealing step inside of a glass ampoule. Detailed analysis and structural investigation using X-ray powder diffraction (PXRD) indicate that Ag2CdGeSe4 crystallizes in the wurtzstannite-type structure with space group Pmn21. For Rietveld refinements, all cubic diamond/sphalerite- and hexagonal diamond/wurtzite-related structure types including all subgroups of the wurtzstannite-type structure were considered. Quantum-chemical calculations were carried out at density-functional theory (DFT) level. The results do not allow an unambiguous verification of the experimentally observed Ag2CdGeSe4 type, due to the small energy differences between the structures. Comparison of calculated and measured UV/Vis data, however, support the results of the Rietveld refinement.