Abstract
The mechanical stability of oxides formed on metallic alloys is a key concern in the determination of component susceptibility to the medium in contact and the applicability of the alloy to high temperatures and other extreme conditions. In this context, the energy of adhesion is a key parameter. Density functional Theory (DFT) and other atomistic methods are fundamental tools in the determination of this quantity for Metal/Oxide interfaces. In this paper Fe(BCC) / Magnetite interface is assessed within the DFT approach. This system is of general interest, given that magnetite (Fe3O4) is the oxide in direct contact with the metal under generalized corrosion and for a wide range of conditions. Moreover, it has been demonstrated that passive films on iron alloys exhibit similar structural properties. Magnetite is an inverse spinel with Fd3m structure, while Iron has a BCC crystal structure. The interface Fe3O4[001]-Fe[001] is modeled. The orientation relationship experimentally observed for this interface is Fe3O4[100]||Fe[110]. In the (001) direction, atomic layers with compositions FeO2 and Fe are alternated. Here only the Fe termination is treated, as it has been proved that it constitutes the most stable interface [11 FORTI, M.D., ALONSO, P.R., GARGANO, P.H., et al., “A DFT study of atomic structure and adhesion at the Fe(BCC)/Fe3O4 interfaces”, Surface Science, v. 647, pp. 55–65, 2016.,22 FORTI , M., ALONSO , P., GARGANO , P., et al.,“Adhesion Energy of the Fe(BCC)/Magnetite Interface within the DFT Approach” , Procedia Materials Science, v. 8, pp. 1066–1072 2015.]. DFT is used to calculate the work needed to relatively slide the oxide and metal surfaces in reference to the principal directions of the interface. Hence, it is possible to calculate the interface potential according to the model by WEI and HUTCHINSON [33 JIANG, Y., WEI, Y., SMITH, J.R., et al.,“First principles based predictions of the toughness of a metal/oxide interface” , International Journal of Materials Research (Formerly Zeitschrift Fuer Metallkunde), v. 101, n. 1, pp. 8–15 2010.]. This potential can be used for construction of meso scale models of the interface for a complete study of its properties.
Keywords
Interface Adhesion; Interface Potential; Magnetite; DFT
