ELECTRONIC-PROPERTIES OF THE ORDERED DELAFOSSITE-TYPE SUPEROXIDES YCUO2+DELTA

Electronic-structure calculations have been carried out on the ordered delafossite-type superoxides YCuO2+delta (0.5 less than or equal to delta less than or equal to 0.7) that Cava et al. have synthesized recently by inserting interstitial O into the triangular Cu planes of YCuO,. The results exhibit a unique feature where each interstitial O inserts two half-filled, cluster-derived Cu3O7 ''impurity levels'' into the similar to 2.7-eV semiconductor gap of YCuO2. These levels evolve into half-filled ''impurity bands'' as adjacent clusters are corner-linked to form continuous one-dimensional (1D) linear (delta approximate to 1/2) and 2D planar (delta approximate to 2/3)networks that may exhibit interesting transport and magnetic properties.