Figure 3
From: Massive Interfacial Reconstruction at Misfit Dislocations in Metal/Oxide Interfaces
(a) Change in energy of the system with the introduction of defects: (a) vacancies; (b) interstitial oxygen; (c, d) mixture of vacancies with twelve and seventeen interstitial oxygen for (c) and (d), respectively. At any stage, the vacancy concentration at the interface was calculated as the ratio of the total number of iron vacancies introduced at the interface with respect to the total number of iron sites present at the interface within the ideal structure. In Fig. 3a the Fe/O ratio was calculated from the number of iron left at the interface at any stage divided by the number of oxygen atoms within the interfacial yttria layer. For the calculation of the Fe/O ratio in Fig. 3b and Fig. 3d both interstitial oxygen and oxygen atoms within the interfacial yttria layer were considered. The capital letters indicate various structures used for subsequent calculations. M is the ideal structure with no defects (vacancy or interstitials) while N and Q are the structures with twelve and seventeen interstitial oxygen (with no vacancies), respectively. In Fig. 3(b) the indicated oxygen chemical potentials are computed for T = 900K. The insets are zoomed-in regions of the curves indicated by the dashed-line boxes. In the insets, points A, B and C represent the vacancy concentration corresponding to the minimum energy structures for the zero, twelve and seventeen-oxygen structures. For the minimum energy structures (A, B and C) all iron vacancy formation energies are positive and any additional iron vacancies increase the energy of the system. In all cases, the associated change in the atomic structure lowers the Fe/O ratio at the interface, restoring the chemical imbalance.
