BORN MODEL CALCULATION OF DEFECT ENERGIES IN CAF2

A general formulation of the Born model as applied to the calculation of the energies to form point defects in ionic crystals is given, and then specialized to vacancies and interstitials of both kinds in CaF2. After examination of the effects produced by several factors in the calculation, 'best' values are chosen for the formation energies. These are used to compute the energies to form anion Frenkel pairs (2·7 ± 0·4 eV pair), cation Frenkel pairs (7·5 ± 0.8 eV pair) and Schottky trois (5·1 ± 0·7 eV trio). The results are in reasonable agreement with Ure's experimental results, which indicate that anion Frenkel pairs are the equilibrium defects in CaF2, with a formation energy of 2·8 eV. © 1968.