Oxygen stoichiometry disordering, and the orthorhombic-to-tetragonal transition inYBa2Cu3O7−δ

Abstract

A mean-field theory for oxygen unloading and disordering is presented as a model for the orthorhombic-to-tetragonal (OT) transition in $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$. The results successfully match the stoichiometry and ordering measured by thermal gravimetry and neutron powder diffraction structural refinements. The O(1) or O(5) site energy at infinite dilution is found to be -3.73 eV, the O(1)-O(5) interaction energy is 0.09±0.003 eV, and the twin plane energy is estimated to be 2.2×${10}^{-2\mathrm{}}$ J/${\mathrm{m}}^2$.