First-principles determination of ferroelectric instabilities in Aurivillius compounds

The microscopic origin of ferroelectric instabilities in Aurivillius compounds is investigated from first principles using the full-potential linearized augmented plane-wave method. A comparative study of the ferroelectric instabilities in archetype materials like Bi2WO6, SrBi2Ta2O9, and Bi4Ti3O12 is investigated by a lattice-dynamics study of the paraelectric phase using the frozen-phonon approach. An analysis of the different displacement patterns displayed by the resulting unstable phonon modes gives insight into the microscopic origin of the ferroelectric transition and the different polarization behavior of the materials.