Seven new quaternary metal sulfides, KY2CuS4, KNd2CuS4, KSm2CuS4, KTb 2CuS4, KHo2CuS4, K 2Dy4Cu4S9, and K2Ho 4Cu4S9, were prepared by the reactive flux method. All crystallographic data were collected at 153K. The isostructural compounds KLn2CuS4 (Ln=Y, Nd, Sm, Tb, Ho) crystallize in space group Cmcm of the orthorhombic system with four formula units in cells of dimensions (Ln, a, b, c (Å)): Y, 3.9475(9), 13.345(3), 13.668(3); Nd, 4.0577(3), 13.7442(10), 13.9265(10); Sm, 4.0218(4), 13.6074(14), 13.8264(14); Tb, 3.9679(5), 13.4243(17), 13.7102(18); Ho, 3.9378(3), 13.3330(11), 13.6487(11). The corresponding R1 indices for the refined structures are 0.0197, 0.0153, 0.0158, 0.0181, and 0.0178. The isostructural compounds K2Dy4Cu4S9 and K2Ho 4Cu4S9 crystallize in space group C2/m of the monoclinic system with two formula units in cells of dimensions (Ln, a, b, c (Å), β (°)): Dy, 13.7061(13), 3.9482(4), 15.8111(15), 109.723(1) ; Ho, 13.6760(14), 3.9360(4), 15.7950 (16), 109.666(2). The corresponding R 1 indices are 0.0312 and 0.0207. Both structure types are closely related three-dimensional tunnel structures. The tunnels are filled with bicapped trigonal-prismatically coordinated K atoms. Their anionic frameworks are built from LnS6 octahedra and CuS4 tetrahedra. KLn2CuS4 contains ∞1[CuS 35-] chains of vertex-sharing tetrahedra and K 2Ln4Cu4S9 contains ∞1[Cu4S812-] chains of tetrahedra. K2Ho4Cu4S9 shows Curie-Weiss paramagnetic behavior between 5 and 300K, and has an effective magnetic moment of 10.71μB for Ho3+ at 293K. Optical band gaps of 2.17eV for KSm2CuS4 and 2.43eV for K2Ho4Cu4S9 were deduced from diffuse reflectance spectra. A first-principles calculation of the density of states and the frequency-dependent optical conductivity was performed on KSm2CuS4. The calculated band gap of 2.1eV is in good agreement with the experimental value.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry