Adhesion and electric structure at Fe3O4/FeCr2O4 interface: A first principles study

Highlights: • Model E has the largest adhesion work and the smallest interface distance. • The interfacial fracture toughness of Model E is between the fracture toughness of bulk Fe₃O₄ and that of bulk FeCr₂O₄. • This model is the actual atomic configuration in the process of oxide scale growth. • Ionic/covalent and metallic bonds are formed at the interface of Model E. -- Abstract: The adhesion energy, interfacial energy, interfacial fracture toughness, electronic structure and valence bond of Fe₃O₄ (001) / FeCr₂O₄ (001) interface have been studied by first principles density functional method. When the number of atomic layers on (001) plane is more than 15 and 13, the Fe₃O₄ (001) and FeCr₂O₄ (001) slabs can reach the characteristics of their respective bulk phases. The effects of different stacking positions on the interfacial bonding and fracture toughness of 12 kinds of interface models with different terminal combinations were studied. The interface configuration Model E which is composed of Fe₃O₄ (001) - FeO termination / FeCr₂O₄ (001) - Fe termination has the maximum adhesion work. The interfacial fracture toughness of Model E is the largest among the interface configurations and is between the fracture toughness of bulk Fe₃O₄ and that of bulk FeCr₂O₄. This model is the most stable in thermodynamics. The electronic structure of the interface indicates that there are ionic/covalent bonds and metallic bonds between the atoms at the interface.