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 in vestigated using first-principles cluster procedures. For the planar C u, a large cluster comprising 74 atoms was studied with both Hartree-F ock and density functional methods. The latter calculations provide fi eld gradients and asymmetry parameters in good agreement with the expe rimental values, The electronic structure revealed by the highest occu pied molecular orbitals is analyzed and discussed. (C) 1998 Elsevier S cience B.V.