Electron density distribution of copper oxides with one-dimensional Cu-O Chain

摘要

We report the charge density distribution p(r) (cheical bounds | PHI (r)|~2; PHI (r) wave function) of Ca_2CuO_3 with the one-dimensional Cu-O chain and (Sr_(0.15), Ca(0.85) CuO_2 with the two-dimensional CuO_2 plane, in comparison with that of superconducting YBa_2Cu_3O_(6.9) with both the -Cu-O- atomic arrangements. p(r) was obtained by the Maximum-Entropy Method (EME) analysis using laboratory X-ray powder diffraction data. The p(r) in (Ca, Sr)CuO_2 is almost spherical, indicating that ionic features are dominant in the CuO_2 planes. This contrasts with the case of supercondcuting YBa_2Cu_3O_(6.9), which shows the remarkable overlapping between Cu 3d and O 2p orbitals. On the contrary, the p(r) in Ca_2CuO_3 indicates the overlapping between Cu and O only along the single chain direction and no interaction between each Cu-O chain.