The technique of the coincidence count rate at the peak of the angular correlation curve (CCR) in positron annihilation was applied to the investigation of vacancy formation energies in thermal equilibrium in nickel, cobalt and iron. The monovacancy formation energy was determined to be 1.55 and 1.34eV for nickel and cobalt, and 1.60eV for α-iron, and 1.40eV for γ-iron, respectively.

Phase Transformations and Vacancy Formation Energies of Transition Metals by Positron Annihilation. H.Matter, J.Winter, W.Triftshäuser: Applied Physics, 1979, 20[2], 135-40