The trapping mechanism of H was investigated by using a molecular dynamics approach. Simulations of the diffusion of this impurity were performed in which Nb-Nb interactions were described by an N-body potential. The parameters of the potential were adjusted to fit the static and dynamic properties of a Nb crystal. The Nb-H interaction was represented by a 2-body potential. The Arrhenius diagram for H diffusion which was predicted by means of molecular dynamics studies in the monocrystalline case involved values of the activation energy which were too small when compared with experimental data. However, the molecular dynamics simulations indicated that there was a large increase in the activation energy in the presence of defects. The effect of imperfections upon H diffusion became less important at about 1000K.

B.Roux, H.Jaffrezic, A.Chevarier, N.Chevarier, M.T.Magda: Physical Review B, 1995, 52[6], 4162-70