Berlin 2018 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 61: Topical Session (Symposium MM): Big Data in Materials Science - Managing and exploiting the raw material of the 21st century
MM 61.3: Vortrag
Donnerstag, 15. März 2018, 16:30–16:45, H 0107
Ab-initio study of the clathrate Ba8 Nix Ge46−x−y y: Stability, structure, and electronic properties — •Martin Kuban, Santiago Rigamonti, Maria Troppenz, and Claudia Draxl — Humboldt-Universität zu Berlin
The type-I clathrate Ba8 Nix Ge46−x−y y is a prototypical example of the phonon-glass–electron-crystal concept and thus promising for thermoelectric applications. Recent experimental studies [1] show that either n- or p-type conductivity can be achieved by tuning its composition around the charge-compensation (x+y=4). This is important in view of building enhanced n-p thermoelectric junctions with the same base material. Upon the addition of Ni, the stable phases tend to form less vacancies (), while the lattice constants stay almost unchanged. In this work we perform an ab-initio cluster-expansion [2] study in the composition range 0 ≤ x ≤ 6 and 0 ≤ y ≤ 4. This allows us to investigate the configurational ground-states (GS) at zero temperature. For these GS-structures, we observed the transition of a minimum in the electronic density of states (DOS) from below the Fermi level for x+y<4, to above the Fermi level for x+y>4, thus confirming the experimentally observed change from n- to p-type conductivity. From the calculation of the phase diagram, we find good agreement with experiment regarding the lattice constant and the formation of vacancies for increasing Ni content.
[1] U. Aydemir et al.; Dalton Trans 44, 7524 (2015).
[2] S. Rigamonti et al., in preparation.