High-Entropy Metal Chalcogenides: A Critical Look at Sublattice Thermodynamics and Structural Flaws

High-Entropy Metal Chalcogenides (HEMCs) are an interesting new group of materials that people are studying for things like thermoelectrics and lithium-ion battery anodes. The main idea is that mixing five or more elements onto the same type of crystal site can create a lot of chemical disorder and lattice distortion, which can lead to some pretty unusual transport properties. A lot of current research papers also use mixing entropy as a major reason for why these complicated materials can stay stable. But if you actually look closely at the local structure of the atoms, they are not completely random. Some atoms seem to have preferences for where they sit and what atoms they sit next to. This review looks at that problem using recent thermoelectric and battery papers. I also talk about some practical problems like short-range order, brittleness, and possible thermal and chemical instability. Finally, I look at how computer simulations could help map out these local structural problems before researchers have to spend large amounts of time testing hundreds of different compositions in a lab.