SYNTHESIS AND CRYSTAL-STRUCTURE OF BA6CU12FE13S27

The new phase Ba6Cu12Fe13S27, a new djerfisherite-like compound, has b een prepared by solid state reaction of BaS3 and CuFeS2 at 1273 K. Thi s compound crystallizes in the cubic system with space group <Pm(3)ove r bar m> (No. 221), Z = 1, and cell constant a = 1037.9(1) pm. The dis crepancy indices of the single crystal structure refinement were R = 0 .023 and R(w) = 0.030. The structure was determined using three-dimens ional single crystal X-ray diffraction data and consists of a three-di mensional cubic framework of edges and corners sharing Cu- and Fe-cent ered tetrahedra forming large interconnecting tunnels and octahedral c ages; one iron atom and a Ba6S octahedron per crystallographic unit ce ll are located in the cages and the channels, respectively, Consequent ly, were found two different geometrical environments for the transiti on metal atoms. XPS analysis reveal the presence of one valence state for copper, Cu(I), whereas iron exists as Fe(II) and Fe(III). (C) 1997 Academic Press.