The diffusion of Ni2+ adatoms on the (001) surface of NiO was deduced from molecular dynamics simulations based upon a rigid ion potential model. A wide reduced-temperature range was covered; from 0.29 to 0.85. Two possible adatom positions were found on the surface in accord with static calculations. From a detailed analysis of the ionic trajectories it appeared that the adatom diffused on the surface via hopping and exchange mechanisms. Both processes exhibited an Arrhenius behavior, for which the corresponding migration energies were deduced. In addition, two distinct temperature regions were found; reflecting different energetic requirements for hopping diffusion. This was due to the spontaneous creation of anionic adatoms that combined with the cationic adatom at high temperatures. Moreover, it was found that although the frequency rates for hopping and exchange were comparable, the exchange mechanisms contributed more than did hopping to the diffusion coefficient; by as much as an order of magnitude at high temperatures.

Cation Adatom Diffusion on the NiO(001) Surface by Molecular Dynamics Simulation. Karakasidis, T.E., Papageorgiou, D.G., Evangelakis, G.A.: Surface Science, 2001, 486[1-2], 46-54