Understanding the Band Engineering in Mg2Si‐Based Systems from Wannier‐Orbital Analysis.

The Mg2Si1−xSnx solid solution is one of the most representative examples of band engineering, in which the thermoelectric performance is significantly improved by the conduction band convergence. The mechanism behind it is simply explained by the chemical differences between Si and Sn. Here a systematically theoretical study is reported based on Wannier function analysis. It is revealed that the band convergence in Mg2Si1−xSnx is actually driven by the variation of lattice constant, since the heavy and light conduction valleys have different dependence on the bonding length. Alternatively, the band engineering can also be achieved by introducing cation dopants to tune the relative strength of the two chemical bonds directly. In Mg2−xSrxSi, a similar band convergence to Mg2Si1−xSnx is predicted by the band structure calculations. This work provides an insightful understanding of the band convergence in Mg2Si‐based materials, and it enables a more efficient and plentiful design for experimental studies. [ABSTRACT FROM AUTHOR]