分子動力学法を用いたパラジウムおよびパラジウム銀合金中の水素拡散特性評価

抄録

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.