The formation energy of an individual cation vacancy in LiF and NaCl was measured by means of the temperature dependence of the electrical signals produced by push-pull deformation of bent crystals and application of the theory of charged dislocations. For LiF the energy was 0.74eV at 680K. For NaCl, the energy was 0.75eV at 627K and 0.72eV at 761K.

Formation Energy of Individual Cation Vacancies in LiF and NaCl. O.S.Spencer, C.A.Plint: Journal of Applied Physics, 1969, 40[1], 168-72