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MM: Fachverband Metall- und Materialphysik
MM 43: Computational Materials Modelling - Alloys II
MM 43.1: Vortrag
Mittwoch, 18. März 2020, 17:15–17:30, BAR 205
Role of disorder in the electronic structure of thermoelectric clathrates — •Maria Troppenz, Santiago Rigamonti, and Claudia Draxl — Humboldt-Universität zu Berlin, Berlin, Germany
Intermetallic clathrate compounds have a huge compositional and configurational space that allows for tailoring their properties towards a high thermoelectric efficiency. For instance in Ba8AlxSi46−x, the configuration of the Al atoms in the crystal framework drastically affects the electronic behavior [1]. This is most strikingly the case at the technologically relevant composition x=16, whose ordered ground state is semiconducting, while disordered structures at higher energies are metallic. An in-depth understanding of this sensitivity of the electronic structure is crucial, since semiconducting behavior is a prerequisite for thermoelectric applications. In this work, we investiage the effects of disorder on the temperature-dependent electronic and structural properties. To this end, we develop a multi-scale approach, based on statistical thermodynamics combined with the cluster-expansion method [2] and ab-initio calculations. We discover a semiconductor-to-metal transition that is accompanied by an order-disorder phase transition at 582 K.
[1] M. Troppenz, S. Rigamonti, and C. Draxl, Chem. Mater. 29, 2414 (2017).
[2] S. Rigamonti, et al., CELL: python package for cluster expansions with a focus on complex alloys. URL: https://sol.physik.hu-berlin.de/cell