Crystal Structures of SrLnCuS_3 (Ln = Gd, Lu)

摘要

The crystal-chemical characteristics of new complex sulfides SrLnCuS_3 (Ln = Gd, Lu) are determined from the data of X-ray powder diffraction patterns. SrGdCuS_3 crystallizes in the orthorhombic crystal system (space group Pnma) and belongs to the Eu_2CuS_3 structure type with the unit cell parameters a = 10.3282(8) A, b = 3.9624(2) A, and c = 12.9364(9) A. The structure of SrLuCuS_3 is orthorhombic: the KZrCuS_3 structure type, space group Cmcm, and unit cell parameters are a = 3.9105(2) A, b= 12.9419(9) A, and c = 10.0191(8) A. A substantial role of crystal-chemical contraction inside the [LnCuS_3] dimeric block in the stabilization of structure types based on Eu_2CuS_3 and KZrCuS_3 is shown.