Synthesis, structure, and optical properties of the quaternary diamond-like compounds I2–II–IV–VI4 (I=Cu; II=Mg; IV=Si, Ge; VI=S, Se)

Abstract

Three new diamond-like compounds with the formula of I{sub 2}−II−IV−VI{sub 4} (I=Cu; II=Mg; IV=Si, Ge; VI=S, Se) have been synthesized via traditional high-temperature solid-state reactions and structurally characterized by single crystal X-ray diffraction analysis. All the three compounds crystallize in the space group Pmn2{sub 1} in the wurtzite-type superstructure with a=7.563(4), b=6.448(3), c=6.179(3) A, Z=2 for Cu{sub 2}MgSiS{sub 4} (1); a=7.953(5), b=6.797(4), c=6.507(4) A, Z=2 for Cu{sub 2}MgGeS{sub 4} (2); a=7.638(4), b=6.515(4), c=6.225(3) A, Z=2 for Cu{sub 2}MgSiSe{sub 4} (3). All atoms in these compounds are tetrahedrally coordinated. Optical diffuse reflectance UV/Vis/NIR spectra indicate that compounds 1 and 2 have the band gaps of 3.20 and 2.36 eV, respectively. Electronic structure calculations using the CASTEP code indicate that they are all direct band gap compounds. - Graphical abstract: Three new diamond-like compounds, Cu{sub 2}MgSiS{sub 4}, Cu{sub 2}MgGeS{sub 4}, and Cu{sub 2}MgSiSe{sub 4}, have been synthesized. All the three compounds crystallize in the space group Pmn2{sub 1} and all atoms are tetrahedrally coordinated. Highlights: • Three new diamond-like compounds Cu{sub 2}MgSiS{sub 4}, Cu{sub 2}MgGeS{sub 4} and Cu{sub 2}MgSiSe{sub 4} have been synthesized. • All ions are tetrahedrally coordinated. • Electronic structure calculations indicate that they are all direct band gap compounds.