Effective atomic charges and charge transport in superconductor lattices

Effective atomic charges in Rba₂Cu₃O₇ compounds (here R stands for yttrium or a rare-earth metal), Tl₂Ba₂Ca₂Cu₃O₁₀, and Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O₁₀ have been determined. In Rba₂Cu₃O₇, the holes are shown to be delocalized primarily on the oxygen-chain sublattice. Two models of charge distribution within the lattices of Tl₂Ba₂Ca₂Cu₃O₁₀ and Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O₁₀ are proposed, which assume the presence of holes at oxygen sites in the Cu(2)-O plane but differ in the occupation of the 3d shell of Cu atoms at the nodes of Cu(1). The atomic charges of Tl, Bi, and Cu(1) on these two latter lattices are possibly controllable. The results obtained are shown to be qualitatively consistent with Hall measurements of the hole concentration and of its temperature dependence in the compounds studied. Fiz. Tverd. Tela (St. Petersburg) 39, 2118–2122 (December 1997)