ELECTRONIC-STRUCTURE AND BOW-CDW STATES OF CUO3 CHAINS

The interplay of structure and bonding is considered for hole-doped an ionic cuprate chains and layers. Based on al analysis of available exp erimental data it is conjectured that the local doping level tends to be close to delta = 0 or delta = 0.5 or delta = 1, where delta is the hole number relative to the Cu 3d state, and that delta approximate to 0.5 is relevant for superconductivity. Estimates for the strongly ani sotropic exchange integrals from LDA band structures for Sr2CuO3 and C a2CuO3 are reported. Exact diagonalization studies for undistorted and distorted chain clusters indicate a weakly correlated stale in CuO3 c hains doped with 0.5 holes.