CRYSTAL-GROWTH AND REINVESTIGATION OF THE CRYSTAL-STRUCTURE OF CREDNERITE, CUMNO2

Single crystals of nearly stoichiometric CuMnO2 were grown using a LiB O2 flux. They crystallize in the monoclinic space group C2/m with cell parameters a = 557.8(6) pm, b = 288.1(2) pm, c = 588.6(7) pm, beta = 104.00(5)degrees and Z = 2. The structure can be described as a close packing of linear [O-Cu-O](3-) groups parallel to the c-axis where Mn- III-ions occupy edge sharing MnO6 octahedra forming layers perpendicul ar to the c-axis. It is closely related to that of delafossite, CuFeO2 , but the Jahn-Teller effect of Mn-III-ions breaks the three-fold symm etry.