Charged dislocations in alkali halides

The possibility of obtaining analytical expressions for the electrical potential produced by a charged dislocation in alkali halides is discussed. The concept of semi-saturated region is introduced for the cases in which a saturated region exists in the crystal. For this semi-saturated region an analytic expression for the potential exists. There is a second region, where it is not possible to obtain analytic solutions. This region can be described mathematically by a second degree polynomial and the semi-saturated region by a function of the form b1' 1n(r/a) + b2. The potentials for dislocations with charges of 6 x 10-3 esu/cm and 1 x 10-2 esu/cm have been obtained. It is found that the size of the semi-saturated region increases when the charge on the dislocation decreases. For the cases that were considered, the size of the semi-saturated region varies from 0.5 A to 12 A, approximately, when the value of the charge varies from 1 x 10-2 to 6 x 10-3 esu/cm. Finally, a discussion concerning the possibility of determining, within this theory, the charge on a dislocation, is presented. (author)