Determination on the Metastable Interface Structure of Nb/MgO(100) Interface

The metastable interface structures between Nb thin films and MgO(100) substrate are investigated using first‐principles calculation. Based on the calculation results of interface separation works for 25 interface models, three metastable interfaces and one stable interface are identified. The growth orientations of Nb films in both the metastable and stable interfaces are found to be Nb[110] and Nb[100], respectively, which align with previous experimental findings. This suggests that it is feasible to predict the metastable interfaces in metal/oxide interface systems by calculating interface energy. Additionally, a comparison is conducted between the stable and metastable interfaces. The metastable interface exhibits a lower interface separation work and lower system energy compared to the stable interface. Herein, it is indicated that the interface separation work plays a key role in determining the metastable interface structure of Nb/MgO(100), rather than the total energy of the entire interface system.