High-throughput exploration of alloying as design strategy for thermoelectrics

We explore a material design strategy to optimize the thermoelectric power factor. The approach is based on screening the band structure changes upon a controlled volume change. The methodology is applied to the binary silicides and germanides. We first confirm the effect in antifluorite Mg₂Si and Mg₂Ge where an increased power factor by alloying with Mg₂Sn is experimentally established. Within a high-throughput formalism we identify six previously unreported binaries that exhibit an improvement in their transport properties with volume. Among these, hexagonal MoSi₂ and orthorhombic Ca₂Si and Ca₂Ge have the highest increment in $zT$ with volume. We then perform supercell calculations on special quasirandom structures to investigate the possibility of obtaining thermodynamically stable alloy systems which would produce the necessary volume changes. We find that for Ca₂Si and Ca₂Ge the solid solutions with the isostructural Ca₂Sn readily forms even at low temperatures.