Regensburg 2013 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 7: Computational Materials Modelling - Methods
MM 7.4: Vortrag
Montag, 11. März 2013, 12:30–12:45, H24
A polarizable potential for the Al2O3-Y2O3 system — •Hannes Guhl, Matthew Foulkes, Michael Finnis, and Paul Tangney — Department of Physics and Materials, Imperial College London, SW7 2AZ, UK
The high-temperature oxidation rate of alloys containing aluminium is much reduced in the presence of rare earth (RE) elements such as yttrium. Apparently, the grain boundaries acting as the primary channel via which oxygen and metal ions cross the oxide film are effectively blocked by the segregating RE elements, yet it is controversial whether or not this “reactive element effect” is due to the alteration of the electronic- or atomic structure.
We apply density functional theory (DFT) as the best available tool for addressing the subtle interplay of defect formation energies and mobilities, including yttrium in grain boundaries of alumina. However, due to their complexity, realistic structural models of grain boundaries cannot be established with DFT alone. Therefore, we present here an empirical, computationally cheap, polarizable ion potential, which matches the DFT interatomic forces in Y doped alumina. We make a direct comparison between computed and experimentally measured grain boundary structures and energies. In addition, the potential captures the essential energetic and structural properties of pure Y2O3 as well as of mixed phases such as Y3Al5O12, suggesting that it will be useful for atomistic studies of the complex thermodynamics across the Al2O3-Y2O3 system.