Effect of strain and oxygen vacancies on the structure of 180^o ferroelectric domain walls in PbTiO_3

TL;DR

This study investigates how strains and oxygen vacancies influence the structure of 180° ferroelectric domain walls in PbTiO_3, revealing that vacancies significantly alter wall structure without affecting thickness.

Contribution

It provides a semi-analytic analysis of strain and vacancy effects on domain wall structure, confirming and extending recent ab initio findings.

Findings

Oxygen vacancies broaden domain walls by about 50%.

Normal and shear strains modify the structure but not the thickness.

Pb-centered domain walls with vacancies are unstable under strain.

Abstract

In this paper we study the effect of normal and shear strains and oxygen vacancies on the structure of 180^o ferroelectric domain walls in PbTiO_3. 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 PbTiO_3. 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 PbTiO_3 show that oxygen vacancies affect the structure of 180^o domain walls significantly but do not have a considerable effect on the thickness of domain walls; they broaden the domain walls by about fifty percent. We also study the effect of normal and shear strains on both perfect and defective 180^o domain walls. We observe that normal and shear strains affect the structure but do not change the domain wall thickness.