Refined Crystal Structures of SrLnCuS3 (Ln = Er, Yb)

Abstract

According to powder X-ray diffraction data, the crystal structures of compounds SrLnCuS₃ (Ln = Er, Yb) have been refined by minimizing the derivative difference in the anisotropic approximation for all atoms. Crystals are orthorhombic, space group Cmcm, structure type KZrCuS₃: a = 3.93128(3) Å, b = 12.9709(1) Å, c = 10.1161(1) Å, V = 515.843(9) ų, ρ_calc = 5.337 g/cm³, Z = 4, R_DDM = 3.73%, R_F = 2.06% (SrErCuS₃); a = 3.91448(4) Å, b = 12.9554(1) Å, c = 10.0332(1) Å, V = 508.842(8) Å3, ρ_calc = 5.487 g/cm³, Z = 4, R_DDM = 3.56%, R_F = 1.48% (SrYbCuS₃). The structure of SrLnCuS₃ is described by [LnCuS₃] twodimensional layers formed by distorted CuS₄ tetrahedra and LnS₆ octahedra with Sr²⁺ ions residing between the layers. The compounds are transparent for IR radiation in the range 3200–1800 cm^–1.