Electronic structure of the Hg-O double-layer compound Hg2Ba2YCu2O8 - art.no. 134506

Hg2Ba2Y1-xCaxCu2O8-delta contains a double HgO layer with a rock-salt struc ture. For x = 0.3, 0.4, and 0.5 the samples have metallic resistance and be come superconductors at low temperatures. The x = 0 prototype is an insulat or. In order to provide the basic ingredients for the understanding of the normal and superconducting properties, the electronic structure of body-cen tered tetragonal Hg2Ba2YCu2O8 has been calculated using the full-potential linear augmented plane wave method, within the local approximation to densi ty-functional theory. States close to the Fermi level (E-F) are characteriz ed by two antibonding Cu-d(x)2-(y)2O1-p bands (one per Cu-O plane) and the presence of another pair, derived from Hg-d-O2-O3-p. The states of Hg-p cha racter, characteristic of mono Hg layer superconductors, are pushed well ab ove E-F. The Hg-d-O-p band is not totally occupied and the resulting hole d oping of the Cu-O planes is dimished from that expected from ionic consider ations.. Our results are compared with the previously obtained electronic s tructure for the isostructural Bi2Sr2CaCu2O8 and Tl2Ba2CaCu2O8 compounds, t o the stoichiometric (delta = 0) one-layer parent compounds of the Hg high- T-c superconductor and in particular with the nearly optimally doped HgBa2C a2Cu3O8+delta, delta = 0.5. Finally, the electric-field gradients at each a tomic site are reported.