First-Principles Approach to Nonlinear Lattice Dynamics: Anomalous Spectra in PbTe

published_or_final_versio

The Accurate Computation of the Negative Curie Temperature of PbTe

Session 11: Bulk Materials 1 - Oral Presentatio

The Anharmonic Origin of the Paraelectric Phase Transition in PbTe

Sa4C Session: Bulk - no. Sa4C3 - Oral Presentatio

Atomic simulations of nonlinear lattice dynamics in PbTe

Session M16: Focus Session: Computational Studies of Thermoelectric MaterialsPbTe is of great interest as a thermoelectric material and for displaying signs of strong phonon interactions. Inelastic neutron scattering experiments reveal a signature of strong anharmonicity as evidenced in anomalous temperature dependence of the phonon spectra. Here we perform molecular dynamic simulations using a 4th-order interatomic potential deduced from first-principles calculations. The temperature dependent phonon spectra are successfully reproduced from first-principles for the first time. The emergence of a new mode at the zone center is unambiguously shown, as observed in experiment. Furthermore, we confirm that there is not a local spontaneously broken symmetry, clarifying recent controversy among experimental results. Phonon self-energies at different temperatures are computed to show the origin of the phonon anomalies

New class of planar ferroelectric Mott insulators via first-principles design.

The bulk photovoltaic effect requires a low electronic band gap (i.e., ≈1–2 eV) and large electronic polarization, which is not common in known materials. Here we use first-principles calculations to design layered double perovskite oxides AA′BB′O6 which achieve the aforementioned properties in the context of Mott insulators. In our design rules, the gap is dictated by B/B′ electronegativity difference in a Mott state, while the polarization is obtained via nominal d0 filling on the B-site, A-type cations bearing lone-pair electrons, and A≠A′ size mismatch. Successful execution is demonstrated in BaBiCuVO6, BaBiNiVO6, BaLaCuVO6, and PbLaCuVO6