Diffusion of point defects in ordered and disordered Ni–Fe alloys

We present how the ordered and disordered arrangement of elements can affect the transport properties of point defects in Ni–Fe metallic alloys using atomistic simulations. With molecular dynamics (MD) based on both first-principles calculations and empirical potentials, we show that defect diffusion slows down in the ordered Ni–Fe phases due to the decrease of effective coordination number for nearest-neighbor defect jumps. Thus, the disorder-order transition influences defect migration by changing the local atomic environment. We further elucidate that the defect diffusion in ordered and disordered phases is a result of the interplay between preferential defect diffusion and defect stability that relate to the defect energetics. These results indicate that defect evolution may be significantly delayed by embedding certain ordered structures into bulk disordered alloys, which are important to the understanding of the role of disorder in metallic alloys and provide insights on materials engineering by tuning the disorder/order level.