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MM: Fachverband Metall- und Materialphysik

MM 39: Computational Materials Modelling V

MM 39.9: Talk

Thursday, March 17, 2011, 18:15–18:30, IFW A

Lead-free piezo-electrics: A combined investigation via synchrotron measurements and first-principles calculations — •Sascha B. Maisel, Henry E. Mgbemere, Rodrigo P. Fernandes, Gerold A. Schneider, and Stefan Müller — Hamburg University of Technology, Institute of Advanced Ceramics, Denickestrasse 15, 21073 Hamburg, Germany

We present structural and chemical investigations of lead-free piezomaterials based on perovskite niobates like NaNbO₃, KNbO₃, LiNbO₃ and their multinary compounds from ab-initio calculations. Since some intrinsic properties of these materials (like ferroelectricity) are very sensitive to cell geometry and the precision of relaxations, the choice of the correct super cells and exchange-correlation functionals is crucial. To make the proper choices, we compare the data from density functional theory with experimental data from both single crystals and sintered ceramics, with very good agreement. The cluster expansion formalism is applied to these DFT results in order to obtain concentration resolved information on short range ordering of the materials. Once the proper short range ordering is known, we are able to calculate piezoelectric response tensors for realistic super cells by means of density functional perturbation theory. The eventual aim of these investigations is to give a quantitative description of the electric and piezoelectric behavior as a function of compound concentration.