Regensburg 2019 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 14: Postersession KFM

KFM 14.19: Poster

Wednesday, April 3, 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.