Classical and Quantum Simulations of Yttrium Cuprate Properties

Abstract

The defect properties of a number of yttrium cuprate materials have been studied with shell-model and quantum mechanical methods. We find that the structures of YBa₂Cu₃O₇, YBa₂Cu₃O_6.5, and YBa₂Cu₄O₈ are reasonably reproduced with a single interatomic potential with deficiencies that are pointed out. Frenkel defects on the oxygen sublattice are the dominant computed defect in those materials. Impurity substitution at particular sites has been studied with a quantum mechanical model. In the case of Ca²⁺ substitution for Y³⁺, there is a sharp reduction in the ionization potential for formation of delocalized holes in the CuO₂ plane.

Key Words:

• Yttrium cuprate
• Frenkel
• Schottky
• impurity
• shell-model
• Hartree-Fock