90-degree Ferroelectric Domains in PbTiO3: Experimental Observation and Molecular Dynamics Simulations

TL;DR

This study combines experimental TEM observations and molecular dynamics simulations to investigate 90-degree ferroelectric domains in PbTiO3, revealing their metastable nature and stability mechanisms, and contrasting them with BaTiO3.

Contribution

It provides the first combined experimental and computational analysis of 90-degree domains in PbTiO3, highlighting their metastability and the role of polarization-strain coupling.

Findings

90-degree domains observed in PbTiO3 via TEM.

Simulations show these domains are metastable and arise during cooling.

Such domains are energetically unfavorable in BaTiO3 under normal conditions.

Abstract

We report observation of 90-degree ferroelectric domain structures in transmission electron microscopy (TEM) of epitaxially-grown films of PbTiO3. Using molecular dynamics (MD) simulations based on first-principles effective Hamiltonian of bulk PbTiO3, we corroborate the occurance of such domains showing that it arises as metastable states only in cooling simulations (as the temperature is lowered) and establish characteristic stability of 90-degree domain structures in PbTiO3. In contrast, such domains do not manifest in similar simulations of BaTiO3. Through a detailed analysis based on energetics and comparison between PbTiO3 and BaTiO3, we find that 90-degree domain structures are energetically favorable only in the former, and the origin of their stability lies in the polarization-strain coupling. Our analysis suggests that they may form in BaTiO3 due to special boundary condition and/or defect-related inhomogeneities.