SYNTHESIS, CRYSTAL-STRUCTURE, AND ELECTRONIC-STRUCTURE OF CSCUFES2

The new chalcogenide CsCuFe2 has been prepared by solid state reaction of stoichiometric amounts of CuFeS2 and Cs2CO3 at 1280 K. This phase crystallizes in the ThCr2Si2-type structure with space group I4/mmm (N o. 139), Z = 2, and cell constants a = 394.2(1) pm, and c = 1423.8(9) pm. The discrepancy indices of the single-crystal structure refinement were R = 0.054 and R(w) = 0.050. The sulfur atoms form layers of edge -sharing square pyramids pointing up and down with their apices. The C u and Fe atoms are located in the remaining tetrahedral holes, while t he Cs atoms are found in the interlayer region coordinated to eight su lfur atoms, forming a cube elongated along the c axis. The electronic structure is analyzed by means of extended Huckel tight-binding calcul ations. Our results show that this compound should be a metal and that the interactions between the transition metals atoms are largest for Fe-Fe pairs. (C) 1996 Academic Press, Inc.