2018 Volume 67 Issue 2 Pages 235-241
Hydrogen diffusion in Pd with various H concentrations and Pd-Ag alloys with various Ag and H concentrations is investigated using molecular dynamics simulations. At H concentration of 0.5 in Pd, the miscibility gap caused by the spinodal decomposition is observed. The diffusion coefficient of H in Pd is kept constant at H concentration less than 0.1, then increases with increasing H concentration until the phase transition occurs, and after reaching a maximum it decreases with increasing H concentration. The simulations of varying a temperature predict the activation energy for H diffusion of 0.163 eV at H concentration of 0.05, which agrees well with that reported in the literature, and minimum activation energy of 0.144 eV at H concentration of 0.5. Moreover, our results indicate that the addition of Ag to Pd leads to the dissipation of the miscibility gap. The diffusion coefficient of H in Pd-Ag alloys significantly decreases with increasing Ag concentration. The minimum activation energy for H diffusion in Pd-Ag alloys is estimated to be 0.135 eV when Ag and H concentration are 0.1 and 0.5, respectively.
