Atomic Charges in YBa2Cu3O7, YBa2Cu4O8, and Y2Ba4Cu7O_(15) Ceramic Samples

摘要

The atomic charges in the YBa2Cu3O7, YBa2Cu4O8, and Y2Ba4Cu7O_(15) lattices have been determined by comparing the experimental and calculated parameters of the crystal electric-fleld-gradient tensors. It has been demonstrated that the holes in these lattices are localized at oxygen ions around the Cu ions in the CuO3 chains. These results are in agreement with the model according to which the interaction between electrons and two-atom two-electron centers with a negative correlation energy is considered as the mechanism responsible for high-temperature superconductivity.