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 P2(1)/c of the monoclinic system in a cell at 153 K of a = 6.2712 (6) angstrom, b = 17.947 (2) angstrom, c = 7.4901 (8) angstrom, beta = 120.573 (1)degrees, and V = 725.81 (12) angstrom(3). The structure contains two-dimensional (2)(infinity)[CuSbS3] layers separated by K atoms. Each (2)(infinity)[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 angstrom above the plane of the S atoms. Each Sb atom is similarly coordinated to three S atoms but is about 1.1 angstrom above its S-3 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 10) crystal face of a red block-shaped crystal of K2CuSbS3 indicates an experimental indirect band gap of 2.2 eV. (c) 2005 Elsevier Inc. All rights reserved.