Synthesis, crystal structure and physical properties of a novel quaternary selenide Cu6GeWSe8

Here we report a novel quaternary selenide Cu6GeWSe8 synthesized directly from the constituent elements, which forms within the temperature range from 460 to 620 degrees C. It crystallizes in the space group P6(3)mc with two formula units in the cell of dimensions a = 7.8651 (5) angstrom, c = 12.9275 (6) angstrom. In the unit cell composed of MSe4 (M = Cu, Ge and W) tetrahedrons, Cu atoms occupy two sets of 6c Wyckoff positions, Ge and W atoms respectively occupy 2a and 2b positions, while Se atoms are located at four inequivalent sites, respectively 2b (Se1), 6c (Se2), 6c (Se3) and 2a (Se4). The electrical resistivity and Vis-Nir absorption spectrum indicate that the compound exhibits a semiconducting behavior with an optical band gap of 1.586 eV Cu6GeWSe8 shows diamagnetism at room temperature and the emergence of a Curie-Weiss-like tail at low temperature. The band structure calculation demonstrates that the title compound has a direct band gap, and Cu and Se atoms dominantly contribute to the energy bands and density of states. Cu is mostly in 3d(10) state (+1 valence) and Se in 4p(6) state (-2 valence). On the basis of the experimental and calculation results, it is concluded that Cu6GeWSe8 is a diamagnetic direct-gap semiconductor.

Automated summary

A novel quaternary selenide Cu6GeWSe8 has been synthesized from the constituent elements, showing semiconductor behavior with a direct band gap. The compound exhibits diamagnetism at room temperature and has a direct band gap, with Cu and Se atoms playing a dominant role in the energy bands and density of states.