Cluster calculations of the hyperfine properties of copper compounds

Spin-polarized ab-initio cluster procedures are used to investigate the ele ctronic structure of CuO2-planes in the La2CuO4 and YBa2Cu3O7 compounds. In particular, electric field gradients (EFGs) and magnetic hyperfine interac tion parameters for the Cu sites were calculated with various theoretical m ethods. Calculations with density functional theory reproduce the experimen tally determined EFGs fairly well while those at the Hartree-Fock level gen erally yield values which are too large by about 40%. The anisotropic magne tic hyperfine coupling can also be calculated with reasonable accuracy.