Electronic Structures and Properties of the Charged Model Clusters Relating to High-Tc Superconductor YBa2Cu3O7-x

摘要

We have carried out an extended huckel calculation to rationalize the role of CuO3 chains and the size effect of the charged model clusters for the following charged model culsters : Cu6O2128-, Cu6O2230-, Cu9O3039-, Cu9O3243-, Cu12O3848-, Cu15O5065-, Cu18O5466-, Cu18O5568-, Cu24O7084-, and Cu27O7893- for high-Tc superconductor YBa2Cu3O7; Cu6O1822-, Cu9O2631-, Cu12O3236-, Cu15O4249-, Cu18O4650-, Cu24O6064-, and Cu27O6669- for insulator YBa2Cu3O6. The results show that the electronic structures and properties of the charged model clusters relating to high-Tc superconductor are very sensitive to the size change of the clusters with various environmental effects, wherease those of the charged model clusters for insulator YBa2Cu3O6 are monotonous to the size change. The CuO3 chains along the b-direction may yield cooperative electronic coupling with the CuO2 layers in determining both conducting and superconducting properties of YBa2Cu3O7-x system.