Effect of Σ5(2 1 0)[0 0 1] symmetric tilt grain boundary on the compatibility between iron and liquid lithium: Atomistic simulations

The compatibility between Fe-based alloys and liquid Li is crucial for the development of liquid Li blanket in the fusion devices. In this work, molecular dynamics (MD) simulations have been used to reveal the effect of Σ5(210)[001] symmetric tilt grain boundary (GB) on the compatibility between Fe and liquid Li. The results show that the corrosion of Fe bicrystal by liquid Li aggravates with increasing temperature, and the critical temperature for the deterioration of compatibility is about 800 K. In the corrosion process, the Fe atoms near the GB are most likely to escape or even dissolve, and Li atoms preferentially penetrate into the intergranular space along the GB. Based on the simulation, the Fe atoms near the GB have high potential energy and poor structural ordering, and their thermal motion at high temperatures generates a large number of Frenkel defects here, which in turn promote the diffusion of Fe and Li atoms along the GB. In terms of energetics, the lower vacancy formation energies and Li atomic substitution energies near the GB are responsible for the GB corrosion.