Mechanism of Ion Movement in Alkali Halides

The energies of ion migration in KCl through isolated vacancies, vacancy pairs, trivacancies, and interstitials have been investigated. A path-variation study in the case of vacancy and vacancy-pair mechanisms show that the usually assumed path in the (100) plane is the most probable one. Trivacancies do not seem to contribute to high-temperature conduction. On the other hand, the formation of a Frenkel defect pair and interstitialcy migration through a collinear path may be responsible for the nonrandom deviations in ionic conductivity data at high temperatures.