Cation vacancy diffusion mechanisms occurring on the NiO(001) surface, together with their corresponding migration energies, were studied (table 22). Using a rigid ion potential and molecular dynamics simulations it was found that the cation vacancy diffusion was the main diffusion process in this surface employing the simple and two different double hopping mechanisms. Although the hopping rates of the latter were about two times lower than that of simple jumps, at high temperatures their contribution to the total vacancy diffusion coefficient was comparable with that of simple jumps. In addition, for all mechanisms saturation was found in the Arrhenius diagrams above 2850K. This behavior was attributed to collective and correlated movements of the surface atoms that were activated from multi-phonon processes above this temperature.

Cation Vacancy Diffusion on the NiO(001) Surface by Molecular Dynamics Simulations. Karakasidis, T.E., Evangelakis, G.A.: Surface Science, 1999, 436[1], 193-201

Table 22

Cation vacancy diffusion on NiO(001)