The hole distribution in cuprate chains

The electronic structure of the prototypical corner-sharing Sr2CuO3 linear chain compound is investigated by combining several theoretical and experim ental techniques. Band structure calculations within the local density appr oximation and using a local orbital basis provided the relevant orbitals an d the transfer integrals for a four-band extended Hubbard pd-model, which w ens treated by means of exact diagonalization and of quantum Monte Carlo ca lculations for finite chain clusters. The band structure values of the tran sfer integrals t(pd) exceed the corresponding values for layered cuprates. Enhanced values of the intersite Coulomb interaction, V-pd = 2 ... 2.5 eV, and a difference between the onsite energies of side and chain oxygen Delta (pp) = 0.5 ... 0.75 eV are deduced from the comparison of the model studies with the intensities of polarization dependent x-ray absorption spectra. T he latter reflect the hole distribution over the oxygen sites.