Predictive Simulation of Diffusion in Ni-Based Alloys Using Pair Interaction Based Kinetic Monte Carlo Method

Investigation of diffusion process in Ni-based alloy is a problem of high relevance in the area of understanding corrosion behavior. We explored the use of a combined approach consisting of density functional theory to compute migration barriers and Kinetic Monte Carlo method to evaluate hard to measure tracer diffusion coefficients. A major challenge in the implementation is the need to find one by one the rate constants for each diffusion process that can occur in the alloy. To overcome this, a pair interaction model was utilized to evaluate the influence of local environment on the kinetic parameters. Previous application of this approach yielded self-diffusion coefficients in pure Ni and the tracer diffusivity of dilute Al in the Ni host that are in good agreement with available experiments. The method was extended to examine oxygen diffusivity in pure Ni and the results show good agreement with values obtained using electrochemical and potentiometric techniques. The presence of Al was found to have a dragging effect on the mobility of oxygen.