Effect of strain and oxygen vacancies on the structure of 180° ferroelectric domain walls in PbTiO3

In this paper, we study the effect of normal and shear strains and oxygen vacancies on the structure of 180° ferroelectric domain walls in PbTiO3. It is known that oxygen vacancies move to the domain walls and pin them. Hence, we assume a periodic arrangement of oxygen vacancies on both Pb-centered and Ti-centered domain walls in PbTiO3. We use a semi-analytic anharmonic lattice statics method for obtaining the relaxed configurations using a shell potential. In agreement with recent ab initio calculations, we observe that a Pb-centered domain wall with oxygen vacancies is not stable even under strain. Our semi-analytic calculations for PbTiO3 show that oxygen vacancies affect the structure of 180° domain walls significantly but do not have a considerable effect on the thickness of domain walls; they broaden the domain walls by about 50%. We also study the effect of normal and shear strains on both perfect and defective 180° domain walls. We observe that normal and shear strains affect the structure but do not change the domain wall thickness.