Extended Data Fig. 8: Atomic displacement maps along both in-plane pseudo-cubic directions.
From: Electron ptychography reveals a ferroelectricity dominated by anion displacements
The vector maps show large displacements of the cation centroids with respect to the centroid of the oxygen anions - (a, d) for Nb atoms and (b, e) for Na atoms, and form the two physical dipoles in the system. The polarization is predominantly in-plane with a small out of plane component. In contrast, the displacement of one cation sublattice with respect to the other (c, f) is much smaller and accounts for a very small fraction of the total polarization. The above displacement maps emphasize the importance of accurately measuring the oxygen atom positions for an accurate characterization of the polarization.
