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Published October 3, 2006 | Published + Supplemental Material
Journal Article Open

The ferroelectric and cubic phases in BaTiO_3 ferroelectrics are also antiferroelectric


Using quantum mechanics (QM, Density Functional Theory) we show that all four phases of barium titanate (BaTiO3) have local Ti distortions toward <111> (an octahedral face). The stable rhombohedral phase has all distortions in phase (ferroelectric, FE), whereas higher temperature phases have antiferroelectric coupling (AFE) in one, two, or three dimensions (orthorhombic, tetragonal, cubic). This FE–AFE model from QM explains such puzzling aspects of these systems as the allowed Raman excitation observed for the cubic phase, the distortions toward <111> observed in the cubic phase using x-ray fine structure, the small transition entropies, the heavily damped soft phonon modes, and the strong diffuse x-ray scattering in all but the rhombohedral phase. In addition, we expect to see additional weak Bragg peaks at the face centers of the reciprocal lattice for the cubic phase. Similar FE–AFE descriptions are expected to occur for other FE materials. Accounting for this FE–AFE nature of these phases is expected to be important in accurately simulating the domain wall structures, energetics, and dynamics, which in turn may lead to the design of improved materials.

Additional Information

© 2006 by The National Academy of Sciences of the USA. Contributed by William A. Goddard III, August 1, 2006. Published online on September 25, 2006, 10.1073/pnas.0606612103. This work was initiated with funding by the Army Research Office (ARO, MURI-DAAD19-01-1-0517) and by the National Science Foundation (MRSEC-CSEM-DMR0080065) and completed with funding from Defense Advanced Research Planning Agency (Predicting Real Optimized Materials) through the Office of Naval Research (N00014-02-1-0839). The Molecular Simulation Center computational facilities used in these calculations were provided by grants from Defense University Research Instrumentation Program (DURIP)–ARO, DURIP–Office of Naval Research, and National Science Foundation Major Research Instrumentation. Author contributions: W.A.G. designed research; Q.Z. performed research; Q.Z. and T.C. analyzed data; and Q.Z. wrote the paper. The authors declare no conflict of interest.

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Supplemental Material - ZHApnas06table.pdf


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