The compound La5Cu6O4S7 has been synthesized by the reaction of La2S3 and CuO in a KI flux at 1173 K. La5Cu6O4S7 crystallizes in a new structure type in a cell of dimensions a = 5.667(1), b = 15.666(3), c = 17.534(3) Å with four formula units in space group D2h/28-Imma of the orthorhombic system at T = 153 K. The structure comprises [Cu2S2] antifluorite-like and [La10S2O8] fluorite-like layers, and these two kinds of layers stack in turn along the  direction. The La atom is coordinated by a distorted square antiprism of four O and four S atoms, and the Cu atom is coordinated by a tetrahedron of four S atoms. The Cu atom in the [Cu2S2] layer is bonded to neighboring Cu atoms; the Cu-Cu distances vary from 2.5864(7) to 2.965(1) Å. The average oxidation state of the Cu atoms is +7/6. La5Cu6O4S7 is metallic in the  direction, consistent with the results of extended Hückel band structure calculation.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry