The energetic properties of the divacancy defect in face-centered cubic nickel were studied using ab initio calculations based upon density functional theory. The formation and binding enthalpies of the divacancy in the first (1nn), second (2nn) and third (3nn) nearest-neighbor configurations were presented. The results showed that the 1nn divacancy configuration was the most stable with a formation enthalpy H2vf of 2.71eV and a small binding energy H2vb of 0.03eV. In the 2nn configuration, the monovacancy–monovacancy interaction was repulsive, and it vanishes in the 3nn configuration. The migration process of the divacancy in its stable configuration was studied. It was found that the divacancy migrates in the (111) plane by successive rotational steps of 60°. The corresponding migration enthalpy H2vm was predicted to be 0.59eV, about half of that found for the monovacancy. For a better comparison of the present results with high-temperature experimental data, the effects of thermal expansion were analyzed. The results showed that the inclusion of thermal expansion permitted satisfactory reproduction of the experimental predictions.

First Principles Calculations of Vacancy-Vacancy Interactions in Nickel: Thermal Expansion Effects. E.H.Megchiche, C.Mijoule, M.Amarouche: Journal of Physics - Condensed Matter, 2010, 22[48], 485502