First-principles calculation of electric field gradients at the Cu sites in YBa2Cu3O7

The electric field gradients at the Cu sites in YBa2Cu3O7 have been investigated using first-principles cluster procedures. For the planar Cu, a large cluster comprising 74 atoms was studied with both Hartree-Fock and density functional methods. The latter calculations provide field gradients and asymmetry parameters in good agreement with the experimental values, The electronic structure revealed by the highest occupied molecular orbitals is analyzed and discussed. (C) 1998 Elsevier Science B.V.