Dipole order and stability of the ferroelectric and antiferroelectric states in lead zirconate

Coordination polyhedra have been constructed for Pb in a PbZrO2 crystal. It is shown that there is no geometric similarity between the displacements of the lead ions and the dipole moments responsible for the antiferroelectricity, which is generally assumed in calculations of the relative stability of the antiferroelectric and ferroelectric phases in pure PbZrO3 and its solid solutions. The latest data on the atomic structure of phases with the Pbam and Cm2m space groups are used to refine conventional reasoning on the dipole motif of this crystal. It is shown that in the point-dipole model, the antiferroelectric dipole configuration is energetically more favorable than the ferroelectric, which is consistent with the observation conditions for both phases.