Anisotropic diffusion of He in titanium : A molecular dynamics study

We use the molecular dynamics to study the migration of He atom, dimer and trimer in Ti. The migration features of these three He species are shown in this paper. It is observed that the Arrhenius relation can well describe their diffusion. However, the diffusion is significant anisotropic. This anisotropy is represented by that the prefactor of the diffusion coefficients are quite different for these He species diffusing in different directions, but the activation energies are the same. Another counterintuitive observation is that He-dimer migrate more quickly than single He atom does. The results emphasize the importance of dynamics simulations in predicting diffusion behavior of He in metals.