Regensburg 2019 – wissenschaftliches Programm
KFM 14.19: Poster
Mittwoch, 3. April 2019, 16:00–18:30, Poster C
Structural and many-body effects in the linear and nonlinear optical response of KNbO3 from ab initio calculations — •Falko Schmidt, Arthur Riefer, Wolf Gero Schmidt, and Arno Schindlmayr — Universität Paderborn, Paderborn, Germany
Potassium niobate (KNbO3), a perovskite-structure ferroelectric, is widely employed in nonlinear optical applications. Because of its small unit cell, KNbO3 is ideally suited to assess the performance of ab initio computational methods for nonlinear optical materials that can be extended to related, more complex materials. After a careful structure optimization, we calculate the linear and nonlinear optical response of KNbO3 in the structurally simple cubic and tetragonal as well as the technologically important orthorhombic phase. While the Kohn-Sham band structure is corrected by GW self-energy shifts, excitonic effects are incorporated by solving the Bethe-Salpeter equation for the linear response. We find a strong dependence on the underlying atomic structure, especially for nonlinear optical spectra. The latter are also strongly affected by the band corrections from the GW approximation.