The quantum-mechanical calculations of Huntington and Seitz, of Huntington, and of Brooks led to a value of about 1ev for the formation energy of a vacancy in copper. It was shown that, in the light of subsequent experimental and theoretical work, the contributions of the electrostatic self-energy and Fermi energy of the valence electron had to be corrected. These corrections led to a final value of about 2eV.

Energy of Formation of a Vacancy in Copper. H.Amar: Journal of Applied Physics, 1962, 33[2], 666-8