Ab initio MO Studies on the Correlation and Spin Correlation Effects for Copper-Oxygen and Copper-Halogen Bonds in High-T_c Copper Oxide Superconductors

Abstract

The correlation and spin correlation effects for Cu +2 XCu +2 (X=F -1 , Cl -1 and O -2 ) were investigated by the ab initio molecular orbital (MO) method. It is found that these effects are particularly strong for Cu +2 F -1 Cu +2 , while they are rather weak for Cu +2 O -2 Cu +2 . Implications of the ab initio MO results are discussed in relation to the high- T c superconductivity for La-Ba-Cu-O and R-Ba-Cu-O (R=Y, etc.). The working hypotheses derived are applied to the molecular design of organic superconductors.