The formation of crystal defects, such as dislocations, not only leads to large lattice strain but also dramatically modifies the local oxygen environment, which manifests through inserting extra lattice planes or perturbing the sequence of oxygen layers . The role of lattice strain arsing from dislocations in the formation energy of oxygen vacancies in the layered oxide structure is assessed via atomic-scale calculations . The formation energy of oxygen vacancy (E O ) is given by the following equation: