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MM: Fachverband Metall- und Materialphysik

MM 10: Computational Materials Modelling III

MM 10.1: Talk

Monday, March 14, 2011, 15:45–16:00, IFW B

Atomistic simulations of dislocations in strontium titanate — •Pierre Hirel^{1, 2}, Matous Mrovec^{1, 2}, and Christian Elsässer^{1, 2} — ¹Institut für Zuverlässigkeit von Bauteilen und Systemen (IZBS), Karlsruher Institut für Technologie, Kaiserstr. 12, 76131 Karlsruhe (Germany) — ²Fraunhofer-Institut für Werkstoffmechanik IWM, Wöhlerstr. 11, 79108 Freiburg (Germany)

Strontium titanate (STO) is a perovskite oxide whose large dielectric constant makes it an attractive material for modern microelectronic applications. In contrast to the ongoing interest in electrical properties of STO, its mechanical properties came to the attention of the scientific community only in 2000 after a surprising discovery of a ductile-to-brittle-to-ductile transition. It was found that STO can deform plastically at room temperature, but the properties of dislocations mediating the deformation remain up to now a matter of debate.

The present study investigates the properties of dislocations in STO by means of atomistic simulations. The investigations are based on a multi-scale approach that uses both quantum-mechanical first-principles calculations and classical atomistic simulations with a rigid-ion potential. We compute the core structures of both screw and edge dislocations and analyze possible dissociation types and their relation to macroscopic mechanical behavior. The glide of dislocations under applied stress is studied directly by molecular dynamics simulations as well as indirectly using the nudged elastic band method. Our simulation results are compared to high-resolution transmission electron microscopy observations.