Cluster calculations of hyperfine interactions in superconducting copper compounds

This paper discusses first-principles cluster investigations on the electro nic structure of YBa2Cu3O7 and La2CuO4 performed at the University of Zuric h. In particular, electric field gradients have been calculated at the copp er sites and their dependence on applying uniaxial strain is studied. Magne tic hyperfine interactions have been evaluated from spin-polarized calculat ions, and the transfer of spin density from neighboring copper ions is expl ained. An interpretation is given of the nuclear quadrupole resonance spect ra in doped La2CuO4.