Synthesis, structure, and electronic structure of K2CuSbS3

The new compound K2CuSbS3 has been synthesized by the reaction of K2S, Cu, Sb, and S at 823 K. The compound crystallizes in the Na2CuSbS3 structure type with four formula units in space group P21/c of the monoclinic system in a cell at 153 K of a=6.2712a=6.2712 (6) Å, b=17.947b=17.947 (2) Å, c=7.4901c=7.4901 (8) Å, β=120.573β=120.573 (1)°, and V=725.81V=725.81 (12) Å3. The structure contains two-dimensional ∞2[CuSbS3] layers separated by K atoms. Each ∞2[CuSbS3] layer is built from CuS3 and SbS3 units. Each Cu atom is pyramidally coordinated to three S atoms with the Cu atom about 0.4 Å above the plane of the S atoms. Each Sb atom is similarly coordinated to three S atoms but is about 1.1 Å above its S3 plane. First-principles calculations indicate an indirect band gap of 1.9 eV. These calculations also indicate that there is a bonding interaction between the Cu and Sb atoms. An optical absorption measurement performed with light perpendicular to the (0 1 0) crystal face of a red block-shaped crystal of K2CuSbS3 indicates an experimental indirect band gap of 2.2 eV.

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