Coexistence of two types of short-range order in Si–Ge–Sn medium-entropy alloys

• Published in: Communications materials 2022-09, Vol.3 (1), p.1-9, Article 66
• Main Authors: Jin, Xiaochen, Chen, Shunda, Li, Tianshu
• Format: Article
• Language: English
• Subjects: 639/301/1023/1026; 639/301/1034/1035; 639/624/399/1099; 639/638/298/917; 639/766/119/1002; Chemistry and Materials Science; Electronic structure; Enthalpy; Entropy; Germanium; Heat of transformation; Heterogeneity; High entropy alloys; Materials Science; Medium entropy alloys; Physical properties; Short range order; Silicon; Tin
• ISSN: 2662-4443; 2662-4443
• DOI: 10.1038/s43246-022-00289-5

Short-range chemical order (SRO) has been shown to play a decisive role in modulating a wide range of physical properties in medium-entropy alloys and high-entropy alloys. The enormous configurational space of these alloys implies multiple forms of SRO may exist, but such structural diversity has not been reported. Here, ab initio-based sampling reveals that Si–Ge–Sn medium-entropy alloys have two distinct forms of SRO, which carry different energies, distinct degrees of local ordering, and dissimilar electronic structures, and co-exist across a wide range of Si–Ge–Sn compositions. We rationalize the co-existence of two SROs through their virtual degeneracy of thermodynamic stability, due to a subtle balance in the change of enthalpy and configurational entropy upon transformation between the two SROs. Such co-existence of SROs suggests an inherent structural heterogeneity, a diffuse electronic structure, and a new route for band engineering in Si–Ge–Sn medium-entropy alloys. More generally, this study indicates possibility of the co-existence of multiple forms of SRO in medium- and high-entropy alloys. Short-range chemical ordering has emerged as a key feature for controlling the properties of high-entropy alloys. Here, ab initio calculations reveal that two types of short-range ordering exist in Si–Ge–Sn medium-entropy alloys, suggesting that multiple types of ordering could exist in a single alloy.