Hochdrucksynthese und Kristallstruktur von Nd4Au2O9 und Gd4Au2O9 / High Pressure Synthesis and Crystal Structure of Nd4Au2O9 and Gd4Au2O9

Abstract

Abstract Single crystals of Nd4Au2O9 and Gd4Au2O9 have been prepared by oxidizing mixtures of gold metal and Nd2O3 or Gd2O3, rsp., with KO2 under high-pressure high-temperature conditions (40 kbar, 1200°C) in a modified Belt-type apparatus. The X-ray structure analyses have been carried out on twinned crystals. The compounds crystallize in the orthorhombic space group Pbcn (Nd4Au,O9: a = 11.938(7) ,b = 6.126(2),c = 11.928(3) A ,Z = 4,1 = 0.0443; Gd4Au2O9: a = 11.922(2), 6 = 6.1242(7), c = 11.917(2) A, Z = 4. R1 =0.0232). The title compounds are isostructural with La4Au2O9. Their structure comprises isolated square-planar AuO4 groups, stacked along [010] to form a columnar structure. The Au-Au distance along the columnar direction is 3.10 Å. Structural relations to Bi2CuO4 und (Nd, Pr)2AuO5 are discussed