Synthesis and the crystal structure of NdCuS₂

Neodymium copper sulfide, NdCuS₂, was synthesized in a single phase by heating the mixture of Nd₂S₃ and CuS in 1: 2 molar ratio in an evacuated quartz ampoule at 1273 K for 4 days. By analyzing its X-ray powder diffraction pattern with the Rietveld method, the detailed data of the crystal structure parameters of the compound were obtained and refined. The atom arrangement in NdCuS₂ was investigated. It was found that NdCuS₂ crystallizes in monoclinic system, space group P2₁/c, and a = 0.6520, b = 0.7169, c = 0.6829 nm, β = 98.48°, Z = 4. NdCuS₂ is isostructural with LaCuS₂, built up of sheets parallel to the b and c axes. One sheet is made of (Nd₄S) tetrahedra and has the composition (NdS); the other is formed by (CuS₄) tetrahedra arranged in pairs, which alternate with pairs of empty tetrahedra. The interatomic distances and the shape of the coordination polyhedra were, however, found to be significantly differed from those of LaCuS₂.