CALCULATION OF THE ELECTRON-DISTRIBUTION OF THE YBA2CU3O7 CLUSTER USING A SCF MADELUNG POTENTIAL

The ab initio unrestricted Hartree-Fock (UHF) method with inclusion of a SCF Madelung potential has been applied to the YBa2Cu3O7 cluster. Mulliken's population analysis and Edward's lattice summation technique are used for the evaluation of the Madelung potential. Approximately equivalent charge distributions on the crystal-symmetry-related atoms have been obtained. The results show that Pa atoms are fully ionized to the form Ba2+, while Y has a net charge +2.63, indicating 0.37 valence electron on it. Y is covalently bound to its neighboring oxygen atoms with moderate strength, hence Y is not strictly separated from the neighboring CuO2 planes, and it may play a significant role as a polarizable subunit.