Complex Roles and Structures of Short-Range Order in Si-Ge-Sn Medium-Entropy Alloy

Short-range order (SRO) has been recently demonstrated to play a crucial role in modulating a wide range of physical properties in medium-entropy alloys (MEAs) and high-entropy alloys (HEAs). However, there is a lack of general understanding of SROs in both their structural diversity and impact of properties in complex concentrated alloys. In this regard, our recent theoretical study^[1] already demonstrated two distinct types of SROs, which carry different energies, distinct degrees of local ordering, and dissimilar electronic structures, can coexist across a wide range of compositions in Si-Ge-Sn MEAs. In further examining the structures and properties of these alloys, we combine first-principle calculations with Monte Carlo sampling, and further develop a highly-accurate, machine-learning interatomic potential. Our study shows electronic, optical, and thermal transport of Si-Ge-Sn alloys can be significantly modulated and engineered through tuning SROs. We further propose an extended descriptor of SRO, by taking into account both its distribution and higher-order effect.<br/><br/>This work is supported by Department of Energy through DE-SC0023412.<br/><br/>1. Jin, X., Chen, S. & Li, T. Coexistence of two types of short-range order in Si–Ge–Sn medium-entropy alloys. <i>Commun Mater</i> <b>3</b>, 66 (2022).