Figure 4. Schematic representation of the ZnO slab used to estimate from DFT calculations the energy formation of Zn and O vacancies.
(a). The distance of a Zn atom from the surface of the slab is represented in the zoom. Evolution of the formation energy of Zn (blue circles) and O (red circles) vacancies versus their distance from the surface of the ZnO slab in oxygen-rich conditions (b). Schematic representation of the core-shell-like model of ZnO nanoparticles illustrating the formation of Zn vacancies at the surface of the nanoparticle (c).
