ALL-ELECTRON AB-INITIO CALCULATIONS OF YBA2CU3O7 WITH SELF-CONSISTENCE CRYSTAL-FIELD

The quantum chemical calculations of cluster YBa2Cu3O7 considering all electrons have been performed by using the ab initio HF method with s elf-consistence crystal field. A Hartree-Fork surface potential is pro posed to make an asymmetric cluster model possess a relatively symmetr ic potential field and td obtain a relatively symmetric electronic str ucture, electronic distributions, frontier orbitals, and bond order, e tc. The suggestions that there exists a covalent bonding complex, [CuO 2- O - CuO - O - Cu-2](68-), in the cell unit of the crystal, and the cell units are connected with each other by ionic bonds along the c di rection of the crystal lattice are offered based on the chemical bondi ng characteristics from the calculated results. The important contribu tion of the apical oxygen to superconductivities is emphasized as well .