The trapping mechanism of hydrogen in niobium was investigated. Simulations of the diffusion process of this impurity were performed in which Nb-Nb interaction was described by an N-body potential (table 17). The potential parameters were adjusted with respect to the static and dynamic properties of a Nb crystal. The Nb-H interaction was represented by a two-body potential. The Arrhenius diagram of the H diffusion coefficient obtained by molecular dynamics in the single-crystal case provided values of the activation energy which were too small in comparison with experimental data. However, molecular-dynamics simulations indicated a large increase of these values in the presence of defects. The influence of imperfections upon the diffusion of hydrogen became less important at around 1000K.Molecular-Dynamics Simulations of Hydrogen Diffusion in Niobium: Influence of Imperfections. Roux, B., Jaffrezic, H., Chevarier, A., Chevarier, N., Magda, M.T.: Physical Review B, 1995, 52[6], 4162-70

Table 17

Hydrogen diffusivity in Nb using two methods