A comprehensive lattice-gas model was developed to predict the diffusivities of dilute H in a wide range of structurally disordered face-centered cubic CuPd alloys with compositions greater than 47at%Pd. Density functional theory was used to perform detailed calculations of H binding energies, vibrational frequencies and activation barriers to local diffusion in 2 representative alloys with 52 and 74at%Pd. These data were used to parametrize all of the 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 these simulations were found to be in good agreement with available experimental data. Kinetic Monte Carlo simulations were also used to investigate the impact of short-range order upon H diffusion in face-centered cubic 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 (9pp)