Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 48: Thermoelectricity

HL 48.2: Talk

Thursday, March 15, 2018, 17:15–17:30, EW 015

Half-Heusler materials : predictions from density functional theory and many-body perturbation theory — •Maedeh Zahedifar and Peter Kratzer — University Duisburg-Essen

For harvesting waste heat at elevated temperature ( T > 400 K), ternary materials with crystal structure C1_b, so-called half-Heusler alloys, have attracted much attention due their high thermal stability and their environmental friendliness. Different exchange correlation functionals (GGA-PBE, HSE06) and the GW approach are used to investigate the effects of these approaches on the band structures and effective masses of six half-Heusler materials with chemical formula ANiSn and ACoSb (A = Zr, Hf and Ti). The GW approach is recommended for Sb compounds in particular, because not only does the position of the valence band maximum change from Γ→ L, but also it strongly affects in thermoelectric properties. In Sn compounds, the conduction band effective mass is underestimated by the HSE06 functional (compared with the GW calculation), but for Sb materials, HSE06 calculations are closer to GW results. Of the six investigated materials, ZrCoSb is determined to be the best thermoelectric material due to its high ZT. After comparing results from different methods for the considered materials, it can be concluded that the simplest method, PBE, is not enough to give conclusive results about thermoelectric properties of investigated materials.