CALCULATION OF EFGS IN HIGH-TC SUPERCONDUCTORS

The electric field gradients (EFGs) at all atomic positions of YBa2Cu3O7 and YBa2Cu3O6 are calculated on the basis of full potential linearized augmented plane wave calculations by an ab initio method. Cood agreement with experimental EFGs is found for all oxygen positions in YBa2Cu3O7 and the Cu1 position in both compounds, while for the Cu2 position in the superconductor the symmetry of the EFG agrees with experiment but the magnitude of our theoretical EFG is only half the experimental value. A small transfer of 0.07 electrons from d(x2-y2) to d(z2) symmetry would be sufficient to achleve agreement with experiment. Thus the underlying local density approximation is not perfect, but remains a very accurate method for describing ground state properties. © 1990 J.C. Baltzer A.G., Scientific Publishing Company.