ATOMIC CHARGES IN RBA(2)CU(3)O(7) SUPERCONDUCTOR LATTICES - ELECTRONIC-STRUCTURE OF THE COPPER ATOMS

The effective atomic charges for all sites of the RBa(2)Cu(3)O(7) latt ices have been found using our Mossbauer data with the Cu-67(Zn-67), B a-133(Cs-133), Eu-155(Gd-155) isotopes, our calculations of the lattic e electric field gradient (EFG) at the lattice sites, as well as the O -17 NMR data available in literature. The charges show holes placed in the chain oxygen sublattice mainly. The Cu2+ Sternheimer factor has b een estimated and the Cu2+ valence EFG in YBa2Cu3O7 has been found. Th e z-axes of the total, lattice, and valence EFG tensors for Cu(2) coin cide with the crystal axis c. For Cu(1) they coincide with the axes b, a, and a, respectively.