Reorientation and degrees of binding of X²⁺-vacancy complexes in KCl

Abstract

The reorientation of impurity-vacancy complexes in KCl crystals doped with Mg 2+ , Ni 2+ , Mn 2+ , Ca 2+ , Sr 2+ , Pb 2+ and Ba 2+ was studied using the ITC method. These results are analysed together with those obtained by other authors by ITC, EPR and optical methods on Cd 2+ , Be 2+ , Eu 2+ , Sm 2+ and Yb 2+ ions. For the first series of ions and Cd 2+ , it was concluded that the most favoured vacancy position is the NNN site, and that it increasingly dominates the NN site as one proceeds from Mg 2+ to Ba 2+ . The observed reorientation of complexes is mainly governed by the vacancy jump from the NNN to the NN position. In the case of Be 2+ it was found that the majority of vacancies are in the NN position and the special behaviour of the Eu 2+ , Sm 2+ and Yb 2+ rare earth ions is discussed.