The method of McKee, Triftshäuser and Stewart was used to determine the vacancy formation energies in copper and silver. The values obtained were 0.98eV for copper and 0.99eV for silver.

Vacancy-Formation Energies in Copper and Silver from Positron Annihilation. J.D.McGervey, W.Triftshäuser: Physics Letters A, 1973, 44[1], 53-4