Development of new kinetic Monte Carlo simulator for hydrogen diffusion process in palladium–silver alloys

A novel kinetic Monte Carlo simulator ‘‘ARC’’ was developed to investigate hydrogen diffusion process in metals and alloys. The results of the hydrogen diffusion coefficients in palladium, silver, and Pd1 xAgx (x 0.5) are in excellent agreement with experimental results. Two different diffusion sites, Pd-rich diffusion site and Ag-rich diffusion site, are found to be necessary to explain diffusion behaviors of hydrogen in palladium–silver alloys. Detailed analysis clarified that hydrogen atoms preferentially diffuse through the palladium-rich region of palladium–silver alloys at low silver concentrations, and that the hydrogen diffusion process at low silver contents is dominated by the jumps in palladium-rich regions. The migration barrier of hydrogen from Pd-rich diffusion site to Ag-rich diffusion site is estimated to be between 0.40 and 0.45 eV.