Molecular dynamics were used to study the migration of He atoms, dimers and trimers in Ti. The migration features of these three He species were shown. It was observed that an Arrhenius relationship could describe well their diffusion. However, the diffusion was significant anisotropic. This anisotropy was reflected by the fact that the pre-factors of the diffusion coefficients were quite different for these He species when diffusing in different directions, while the activation energies were the same. Another counter-intuitive observation was that He dimers migrated more quickly than did a single He atom. The results emphasized the importance of dynamics simulations in predicting the diffusion behavior of He in metals.

Anisotropic Diffusion of He in Titanium: a Molecular Dynamics Study. Chen, M., Hou, Q., Wang, J., Sun, T., Long, X., Luo, S.: Solid State Communications, 2008, 148[5-6], 178-81