| Abstract Scope |
Original vacancy trapping paradigm due to rugged energy landscape in HEAs would lead to sluggish diffusion has been challenged in recent reports, with some indicating anti-sluggish diffusion in BCC HEAs consisting of Group IV elements. This contradiction exposes a major gap in understanding: how does chemical complexity alter atomic transport, and under what conditions does disorder suppress or enhance diffusion? In this work, using DFT calculations, we investigate bond stiffness role on vacancy diffusion. Specifically, we show that on the one hand, Group IV elements (Ti, Zr, and Hf) that induce low bond stiffness reduce vacancy migration barriers, whereas on the other hand, they increase local lattice distortion that create vacancy trapping sites. Conversely, Group VI elements (Mo and W) that have higher bond stiffness raise migration barriers but reduce trapping sites. The impact of the two opposing mechanisms originating due to bond stiffness on vacancy diffusivity is elucidated. |