Effect of Defects and Electric Field on Stress-Induced Motion of 90° Domain Wall in PbTiO₃: A Molecular Dynamics Study

Perovskite ferroelectric crystals are common materials used for actuators utilizing their piezoelectricity. Perovskite materials generally contain ferroelectric domain walls (DWs), whose motion leads to domain switching. As the mobility of DWs is strongly related to the piezoelectric performance, it is essential to understand the mechanism of DW motion in detail. In this study we perform molecular dynamics (MD) simulations with a shell-model interatomic potential for the motion of a \(90^\circ\) DW in PbTiO₃. The reliability of the employed potential has already been confirmed in terms of DW structure and mobility. We simulate the motion of DW induced by stress and investigate the effect of oxygen vacancies and external electric fields. Our simulations demonstrate that the critical shear stress of the motion of DWs having oxygen vacancies is much higher than that of clean DWs, representing the defect hindering domain switching. We also perform ‘multi-physics’ MD simulations, where the combined effect of mechanical stress and electric field is examined. The simulations demonstrate the effect of external electric fields on the stress-induced DW motion to reveal that the critical shear stress of DW motion strongly depends on the direction of the electric fields.