THE CRYSTAL STRUCTURE OF Ni9.54Pd7.46S15

The crystal structure of the synthetic compound Ni 9.54 Pd 7.46 S 15 has been solved and refined to an R-factor of 3.3_. It belongs to the space group Pm 3 m , with a cell edge a of 9.872 A. It is isostructural with the published structures of Pd 17 Se 15 and Rh 17 S 15 . In the structure of Ni 9.54 Pd 7.46 S 15 , Pd is primarily concentrated in the square coordination sites, whereas nickel is concentrated in the flattened tetrahedral and regular octahedral sites. An interpretation of the structure of Ni 9.54 Pd 7.46 S 15 in terms of anioncentered polyhedra reveals features common with pentlandite. Despite the mixed character of the cationic sites, this compound does not appear to be an intermediate member of a hypothetical solid-solution Pd 17 S 15 − Ni 17 S 15 . The stability of Ni 9.54 Pd 7.46 S 15 results from the size fit of the two M–S substructures: a palladium-bearing substructure, with metal–metal bonds, and a nickel-bearing substructure. The site partitioning observed in this structure suggests a similar one for the minor elements (Cu and Hg) in natural palladseite. Because of cation coordinations, the structure is believed to be incompatible with a significant incorporation of divalent iron.