A first-principles study of oxygen vacancy pinning of domain walls in PbTiO3

TL;DR

This study uses density-functional theory to show that oxygen vacancies in PbTiO3 preferentially migrate to and pin 180-degree domain walls, affecting their behavior and stability.

Contribution

It provides first-principles evidence of oxygen vacancy pinning of domain walls in PbTiO3, including detailed pinning energies for different bond orientations.

Findings

Oxygen vacancies have lower formation energy at domain walls than in bulk.

Vacancies tend to migrate to and pin the domain walls.

Pinning energies vary with bond orientation.

Abstract

We have investigated the interaction of oxygen vacancies and 180-degree domain walls in tetragonal PbTiO3 using density-functional theory. Our calculations indicate that the vacancies do have a lower formation energy in the domain wall than in the bulk, thereby confirming the tendency of these defects to migrate to, and pin, the domain walls. The pinning energies are reported for each of the three possible orientations of the original Ti-O-Ti bonds, and attempts to model the results with simple continuum models are discussed.