A comprehensive lattice-gas model was developed in order to predict the diffusivities of dilute H in structurally disordered fcc CuPd alloys containing more than 47at%Pd. Density functional theory was used to perform detailed calculations of H binding energies, vibrational frequencies and activation barriers in alloys containing 52 or 74at%Pd. These data were used to parameterize all possible hopping rates between adjacent interstitial sites in a lattice model for the entire range of compositions. Kinetic Monte Carlo simulations of this lattice model were used to calculate H tracer diffusivities as a function of alloy composition at 400 to 1200K. The results of the simulations were in good agreement with available experimental data. Kinetic Monte Carlo simulations were also used to investigate the impact of short-range order on H diffusion in fcc CuPd alloys. The effects of short-range order were found to be small under conditions of experimental interest.

Ab initio Lattice-Gas Modeling of Interstitial Hydrogen Diffusion in CuPd Alloys. P.Kamakoti, D.S.Sholl: Physical Review B, 2005, 71[1], 014301