Space Charge in Ionic Crystals. I. General Approach with Application to NaCl

Abstract

The defect distribution in an ionic crystal is calculated for both pure crystals and crystals containing divalent cationic impurities. By taking the electrostatic energy into account explicitly, it is shown that bulk electrical neutrality and space-charge regions surrounding the vacancy sources are an inherent aspect of thermal equilibrium. Interactions among defects of the opposite charge are taken into account using the nearest-neighbor-binding model. Inclusion of the long-range effects of the Coulomb interaction and the question of the sign of charged dislocations are discussed.