We perform a first-principles investigation of the role of Coulomb interactions in eight AB${\mathrm{O}}_{3}$ cubic perovskite compounds. The predicted spontaneous polarization and the LO and TO phonon frequencies are found to be in good agreement with experiment. Anomalously large dynamical effective charges give rise to very strong mixing of the mode eigenvectors on going from the TO to the LO case, resulting in a ``giant LO-TO splitting'' in the sense that the soft TO mode is most closely related to the hardest LO modes. The results help explain the extreme sensitivity of these compounds to electrostatic boundary conditions.
This review covers important advances in recent years in the physics of thin-film ferroelectric oxides, the strongest emphasis being on those aspects particular to ferroelectric...
We present a theoretical study of the zone-center optical phonons in wurtzite AlxGa1−xN alloys over the whole compositional range from pure GaN to pure AlN. The phonon modes are...
Phonon excitations play an important role in electronic transport, nonradiative electron-relaxation processes, and other properties of interest for materials characterization, d...
The lattice parameters of KN${\mathrm{O}}_{3}$ were measured in the temperature region of the ferroelectric transition. The changes in the lattice parameters as the crystal unde...
The Larkin-Khmelnitskii theory of uniaxial ferroelectrics is used to derive further predictions for the critical behavior of ferroelectrics, including "local properties" and tra...
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