  Understanding and predicting the dominant diffusion processes in Cr2O3 is
essential to its optimization for anti-corrosion coatings, spintronics, and
other applications. Despite significant theoretical effort in modeling defect
mediated diffusion in Cr2O3 the correlation with experimentally measured
diffusivities remains poor partly due to the insufficient accuracy of the
theoretical approaches. Here an attempt to resolve these discrepancies is made
through high accuracy density functional theory simulations coupled with grand
canonical formalism of defect thermochemistry. In this approach, point defect
formation energies were computed using hybrid exchange correlation functional.
This level of theory proved to be essential for achieving the agreement with
experimental self-diffusion coefficients. The analysis of the resulting
self-diffusion coefficients indicate that chromium has higher mobility at low
temperatures and high oxygen partial pressures, in particular at standard
temperature and pressure conditions. At high vacuum, high temperature
conditions, oxygen diffusion becomes dominant. At Cr/Cr2O3 interfaces O
vacancies were found to be more mobile than Cr vacancies at all temperatures.
Cr diffuses preferentially along the c-axis at low temperatures but switches to
basal plane at higher temperatures. O diffusion is primarily bound to basal
plane at all temperatures.
