Atomistic modeling of the passive film on iron

Atomistic modeling has been used to study the structure and transport properties of surface oxide films on pure iron. These calculations have been used to constrain parameters in the high-field model and diffusion-limited growth model for oxide growth kinetics. Only the Verwey high-field model is found to be consistent with the atomistic modeling, although consistency requires a large interstitial cation concentration. However, if cation transport is dominated by grain-boundary diffusion, the Mott-Cabrera high-field model can be reconciled with the atomistic modeling. Finally, we have considered models of grain ripening and examined the relationship between in-plane grain growth and out-of-plane thickening of the film. If grain ripening is occurring during film growth, then diffusion-limited growth is found to be consistent with empirical data.