Tilt-driven antiferroelectricity in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>PbZrO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>
Konstantin Shapovalov, Massimiliano Stengel
Abstract
Though antiferroelectricity in PbZrO${}_{3}$ was discovered over 70 years ago, there is still no consensus on the exact physical mechanism behind its formation. In this study, the authors rationalize the antiferroelectric $P\phantom{\rule{0}{0ex}}b\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}m$ state of PbZrO${}_{3}$ as a modulated phase, where polarization and antiphase O${}_{6}$ octahedra tilts are coupled via a trilinear gradient term -- the so-called rotopolar coupling. A Landau-like continuum Hamiltonian, with gradient terms calculated directly from first principles, gives an accurate description of the energetics and structure of the $P\phantom{\rule{0}{0ex}}b\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}m$ phase. Besides reconciling the existing theories on PbZrO${}_{3}$, this study may facilitate the understanding of other modulated structures in perovskites, including ferrielectric and incommensurate phases.