Intrinsic and extrinsic defect pairs in caesium halides

Abstract

Interaction energies of cation-anion vacancy pairs and divalent cation impurity-vacancy pairs in caesium halides have been evaluated by means of ionic lattice calculations with a rigorous treatment of the relaxations of ions in the vicinity of the defects. The binding energy of the first associated vacancy pair is lower than the Coulombic value, while that of the second associated pair is close to the Coulombic value. The binding energies of the divalent cation impurity-vacancy pairs vary in the order, third > fourth > second > first associated state, the energy of the second bound pair being close to the Coulombic value.