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The quantum chemical calculations of cluster YBa_2Cu_3O_7 considering all electrons have been per-formed by using the ab initio HF method with self-consistence crystal field.A Hartree-Fork surface potentialis proposed to make an asymmetric duster model possess a relatively symmetric potential field and to obtaina relatively symmetric electronic structure,electronic distributions,frontier orbitals,and bond order,etc.Thesuggestions that there exists a covalent bonding complex,[CuO_2-O-CuO-O-Cu_2]~(6,8-),in the cell unit ofthe crystal,and the cell units are connected with each other by ionic bonds along the c direction of the crys-tal lattice are offered based on the chemical bonding characteristics from the calculated results.The importantcontribution of the apical oxygen to superconductivities is emphasized as well.
The quantum chemical calculations of cluster YBa_2Cu_3O_7 considered all of the electrons have been per-formed by using the ab initio HF method with self-consistence crystal field. A Hartree-Fork surface potentialis proposed to make an asymmetric duster model possess a relatively symmetric potential field and to [0020] [0016] Obtained a relatively symmetric electronic structure, electronic distributions, frontier orbitals, and bond order, etc.Thesuggestions that there exists a covalent bonding complex, [CuO_2-O-CuO-O-Cu_2] of the crystal, and the cell units are connected with each other by ionic bonds along the c direction of the crys-tal lattice are offered based on the chemical bonding characteristics from the calculated results. The importantcontribution of the apical oxygen to superconductivityities is emphasized as well .