Abstract

Hydrothermal syntheses in sealed gold tubes produced four distinct sulfosalts of Pb-Bi-Sb-Au, three of them suitable for crystal structure analysis. They have distinct linear-coordinated Au+ sites in the structure. The crystal structure of Au2Pb20(Sb,Bi)16S45 is composed of two types of rods based on SnS archetype, with Pb atoms on the outer surfaces and predominantly Sb and Bi sites in the rod interior. Lead also occurs in the central portions of the larger rod. Linear-coordinated Au and an additional (Pb,Bi) site are interstitial to the rods. The crystal structure of Au2Pb20(Sb,Bi)16S45 is orthorhombic, space group Cmc21, with lattice parameters a 4.0260(2), b 75.207(7), and c 27.525(1) Å, and unit cell volume 8334.3 Å3. Two structures, Au2Pb12(Bi,Sb)18S40 and Au2Pb22 (Bi,Sb)18S50, are homologues N = 2 and N = 4, of a structural series in which slabs of lillianite structure alternate with wavy (100)PbS layers of incrementally increasing thickness (2 and 4 atomic sheets thick, respectively). Linear-coordinated gold (Au-S distance from 2.20 to 2.46 Å) occurs in the former slabs at the boundary to the latter ones. Unit-cell parameters of Au2Pb12Sb18S40 are as follows: a 4.11(1), b 44.50(1), and c 20.56(1) Å (film data), cell volume 3760.3 Å3, and space group Cmc21. Those of Au2Pb22Sb18S50 are a 4.0876(4), b 55.1514(48), and c 20.4219(11) Å, cell volume 4604.29 Å3, and the same space group. The increment of the b parameter reflects the change in the homologue number N.

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