An atomic interaction interatomic energy is identified in the ABO3 perovskite structure[1]. The term is harmonic in nature and collaboratively couples the antiferroelectric displacement patterns of the A-site cations with O6 octahedral rotations going beyond the traditional Glazer notations. Straightforward analytical derivations using such energy are able to explain the instability of the phonon modes associated with the unusual ground state of the prototype of antiferroelectric materials, that is PbZrO3, as well as their striking atomistic characteristics. Similar derivations further account for the instability of other complex phonon modes in other antiferroelectrics, as well as provide a successful explanation for the occurrence of incommensurability in some perovskite oxides.
References
[1] Kinnary Patel, Sergey Prosandeev, Yurong Yang, Bin Xu, Jorge Íñiguez, and L. Bellaiche. Phys. Rev. B 94, 054107 (2016)