Electrical Property Dominated Promising Half-Heusler Thermoelectrics through High-Throughput Material Computations

Half-Heusler (HH) compounds are one of the state-ofthe-art thermoelectric materials with high electrical properties. The thermoelectric properties (electrical properties and thermal properties) of many HH compounds have not been investigated yet. Therefore, discovery of novel HH compounds with promising thermoelectric properties (intrinsically high power factor and possible low thermal conductivity) is highly needed. Here, we carry out high-throughput computations on 95 (including 75 thermodynamically stable and 20 mechanically stable) HH compounds. Using the thermoelectric properties of experimentally well-studied NbFeSb and ZrNiSn compounds as the screening criterion, we filter out nine p-type and six n-type promising candidates with environmentally friendly and low-cost elements. Scrutinizing their electronic structures, we find that the cooperative effects of high band degeneracy, small deformation potential, light band, and large phonon velocity contribute to the large power factor. (Quasi)harmonic phonon calculations together with the first-principles Debye-Callaway approach are further performed to study their thermal properties. Two compounds (LiZnSb and CaZnGe) possess low lattice thermal conductivity (<4 W m(-1) K-1 at 300 K) owing to strong anharmonic lattice vibrations. However, they are not promising thermoelectric materials due to the poor power factors. The electrical properties dominate the thermoelectric performance in the HH compounds. Considering the excellent electrical properties and relatively low thermal conductivities, three HH compounds (VCoGe, NbCoSi, and TiNiGe) are predicted to be promising thermoelectric candidates. Our work not only provides novel promising materials for future experimental investigation but also offers insights into understanding the underlying physical nature of high thermoelectric performance.