X-Ray Diffraction Study of Lead Sulfide-Arsenic Sulfide Glasses

The structures of arsenic sulfide glass, two synthetic glasses, PbS·5As2S3 and 2PbS·5As2S3, and a natural glass, 5PbS·3As2S3, have been studied by x-ray diffraction. Arsenic is found to have three sulfur neighbors in the first three glasses, just as in crystalline arsenic sulfide. The natural glass and crystalline lead sulfide are similar in that lead is situated in octahedral holes among closely packed sulfurs. The increased ratio of sulfur to arsenic in the natural glass results in four sulfur neighbors for each arsenic. The lead-sulfur distance is about 3.1 A, and that for arsenic-sulfur is about 2.3 A.