2007/12/11 by Craig J. Fennie, Fennie, Craig J., Ram Seshadri +3
Engineering · Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Nuclear materials and radiation effects #Rock Mechanics and Modeling #cond-mat.mtrl-sci
paper · pdf · doi:10.48550/arxiv.0712.1846
arxiv created 2007/12/11 · openalex publication_date 2007/12/11 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The oxide pyrochlore Bi2Ti2O7 is in some ways analogous to perovskite PbTiO3, in that Bi2Ti2O7 has two cations, Bi3+ and Ti4+ in oxidation states that are normally associated with a propensity to off-center. However, unlike PbTiO3, Bi2Ti2O7 is experimentally observed to remain cubic down to 2 K, while the only observed ionic displacements are local and incoherent. Here we report first-principles calculations of the zone-center phonons of the ordered cubic pyrochlore which reveal several lattice instabilities. An analysis of the structural energetics suggest that the ordered cubic pyrochlore is unstable with respect to distortion towards a ferroelectric ground state with a large polarization. Our results suggest a key role of a frustrated soft polar mode in the dielectric properties of bismuth pyrochlores.