Dresden 2011 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 30: Complex Materials

MM 30.2: Vortrag

Mittwoch, 16. März 2011, 16:30–16:45, IFW D

Effective potentials for phonon dynamics in clathrates — •Daniel Schopf and Hans-Rainer Trebin — Institut für Theoretische und Angewandte Physik, Universität Stuttgart, Germany

Intermetallic clathrates are currently actively investigated due to their special thermoelectric properties. They are composed of periodically arranged cages, formed by host atoms, which enclose single guest atoms. The low thermal conductivity of these structures has been attributed to the interaction of the phonons with local vibration modes (“rattling”) of these guest atoms inside the host framework.

For computational studies of dynamic properties long simulation times and large samples are required. This makes first principle calculations of these structures, even with very fast computers, very unfeasible. Classical molecular dynamics, however, can easily handle large systems and long simulation times. The potentials needed for these MD simulations can be obtained from ab-initio calculations with the force-matching method. It uses large numbers of reference data to fit an effective potential that can reproduce the forces, energies and stresses of the ab-initio calculation.

To model the strongly directional atomic interactions in clathrates, angular dependent potentials are required. An analytic potential will be presented to model these systems. The phonon dynamics of clathrates was studied with these potentials and will be compared with ab initio results.