Charge density distribution in alkaline-earth cuprates with one- or two-dimensional arrangements of Cu sbnd O
We report the charge density distribution ϱ(r) ( = |φ(r)| 2 ; φ(r)wave function) of Ca 2CuO 3 with the one-dimensional Cu sbnd 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 sbnd O atomic arrangements. ϱ(r) was obtained by the Maximum-Entropy Method (MEM) analysis using laboratory X-ray powder diffraction data. The ϱ(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 superconducting YBa 2Cu 3O 6.9, which shows remarkable overlapping between Cu 3d and O 2p orbitals. On the contrary, the ϱ(r) in Ca 2CuO 3 indicates substantial overlapping between Cu and O only along the single chain direction and no interaction between each Cu sbnd O chain.