Crystal structure variations in the series SrLnCuS (Ln = La, Pr, Sm, Gd, Er and Lu).

The crystal structures of the complex sulfides SrLnCuS (Ln = Sm, Gd, Er and Lu) have been determined and refined using powder X-ray diffraction. The crystals are found to be orthorhombic, with the structure type changing consecutively in the order BaLaCuS → EuCuS → KZrCuS as the Ln ionic radius decreases in the order La/Pr → Sm/Gd → Er/Lu. Variations of the structure parameters along the series of compounds studied are analyzed, and an effect caused by crystallochemical contraction on the stabilization of the respective structure types is demonstrated.