Intrinsic local symmetry-breaking in nominally cubic paraelectric BaTiO3

TL;DR

This study reveals that cubic paraelectric BaTiO3 exhibits intrinsic local symmetry-breaking displacements, which mimic low-temperature phases and influence its microscopic structure and properties, as shown by DFT calculations.

Contribution

It uncovers the intrinsic, energy-stabilizing local symmetry-breaking displacements in cubic BaTiO3, advancing understanding of paraelectric phase behavior.

Findings

Intrinsic local displacements mimic low-temperature phase symmetries

Displacements act as precursors to thermal motifs in finite temperature dynamics

Symmetry breaking influences microscopic structure and properties

Abstract

Whereas low-temperature ferroelectrics have a well understood ordered spatial dipole arrangement, the fate of these dipoles in paraelectric phases remains poorly understood. Using density functional theory (DFT), we find that unlike the case in conventional non-polar ABO$_3$ compounds illustrated here for cubic BaZrO$_3$, the origin of the distribution of the B site off-centering in cubic paraelectric such as BaTiO$_3$ is an intrinsic, energy stabilizing symmetry breaking. Minimizing the internal energy E of a constrained cubic phase already reveals the formation of a distribution of intrinsic local displacements that (i) mimic the symmetries of the low temperature phases, while (ii) being the precursors of what finite temperature DFT Molecular Dynamics finds as thermal motifs. The implications of such symmetry breaking on the microscopic structures and anomalous properties in these kinds of PE materials are discussed.