Deformation superstructures, tweed, and oxygen-vacancy ordering associated with phase transformations in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{\mathit{z}}$

A theoretical technique is described, employing Monte Carlo simulation, which allows the investigation of strain effects associated with transformations in solids. The method applies a grand canonical stress ensemble in the study of elasticity during phase evolution in ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{\mathit{z}}$ where both oxygen occupancy and atomic positions in the basal plane, as well as total sample volume, can vary. Quenching experiments yield both metastable √2${\mathit{a}}_0$×√2${\mathit{a}}_0$ superstructures from short-wavelength modulations and a tweed texture from long-period 〈110〉 modulations of the ordered z=7.0 compound.