DFT study on Mo-stabilized passive films: Hydroxylation effects on chromium and iron oxide surfaces.

Hydrous Cr 2 O 3 and Fe 2 O 3 surfaces without and with substitutional molybdenum were simulated by DFT modelling to investigate at the atomic scale the role of Mo in improving the corrosion resistance of passive films on stainless steels. The surface structures most energetically favoured were determined in the conditions of interest. For surfaces with a high degree of hydroxylation, the preferential location of substitutional Mo is just under the hydroxyl groups, in agreement with the experimental observations. The substitution by Mo is exothermic and Mo preferentially substitutes in Fe- than in Cr-rich zone of the inner barrier layer of passive films. • DFT modelling of (0001) hydrous Cr 2 O 3 and Fe 2 O 3 surfaces to study passivity. • Determination of energetically favoured terminations in the conditions of interest. • Exothermic substitution by Mo more favoured on Fe 2 O 3 than on Cr 2 O 3 surfaces. • Preferential location of Mo on the surface after highly hydroxylation. [ABSTRACT FROM AUTHOR]