Study of the electronic structure of Zn-doped Y123 ceramics

The electronic structure of undoped and Zn-doped Y123 ceramics is studied b y means of the embedded cluster method at the MP2 electron correlation leve l. The Zn impurity is found to be a source of nonhomogeneity in the hole de nsity distribution in the CuO2 planes which acts as an extended and strong scattering center. In Zn-doped ceramics the orbital symmetry of holes on ne arest-neighbor oxygens is changed: in addition to the 2p sigma symmetry whi ch characterizes the pure material, a 30% contribution of the 2p pi (in pla ne) symmetry is revealed. The latter can hinder the hole-pair formation on oxygen ions.