Structural transformations in nonstoichiometric YBa2Cu3O6+ delta.

Structural-transformation kinetics in YBa 2 Cu 3 O 6+δ caused by oxygen ordering is considered. The effect of long-range interaction between oxygen atoms, Coulomb repulsion, and strain-induced interaction on oxygen ordering is investigated in terms of crystal-lattice-site diffusion theory. Computer simulations of the diffusion of interacting O atoms give a complicated sequence of atomic-scale and mesoscale structural transformations. It is shown that the transformation path strongly influences the crystallographic structure of the ordered phases