Dislocation-induced flexoelectricity in SrTiO$_3$ nanostructure from first principles

TL;DR

This paper investigates how misfit dislocations in SrTiO$_3$ nanostructures induce flexoelectric polarization, revealing the role of pyramidal TiO$_5$ coordination near dislocation cores through first-principles modeling.

Contribution

It introduces a first-principles approach combined with neural-network potentials to study dislocation-induced flexoelectricity in SrTiO$_3$ nanostructures, highlighting the role of local coordination changes.

Findings

Dislocation cores induce significant flexoelectric polarization.

Pyramidal TiO$_5$ coordination forms near dislocation cores.

Theoretical modeling captures the polarization mechanism.

Abstract

Flexoelectricity refers to a linear coupling between the electric polarization and the strain gradient, such as bending or asymmetric compression. This effect is enhanced in nano-scale structures, where grain boundaries or dislocation cores induce the strain gradient. In this study, we theoretically investigate the flexoelectric polarization induced by misfit dislocations in a thin film. A nano-scale dislocation structure is modeled in a periodic SrTiO$_3$ supercell, and then the structure is optimized by using neural-network-potential and first-principles approaches. We point out that a pyramidal TiO$_5$ coordination forms near the dislocation cores, which in turn dominantly causes the sizable flexoelectric polarization.