Significance of the Third-Nearest-Neighbor Divalent CationK+Vacancy Pairs in KCl

Abstract

The identification of the third-nearest-neighbor monoclinic ($C_s$) site comprised of a ${\mathrm{Sm}}^{2+}$-${\mathrm{K}}^{+}$ vacancy pair with the vacancy at the (2,1,1) lattice point in KCl has been made through a high-resolution Zeeman anisotropy fluorescence spectroscopic investigation of several prominent transitions between the ${}_{}{}^5{}_{}{}^{}D$ and ${}_{}{}^7{}_{}{}^{}F$ multiplets. The establishment of the dominant presence of the $C_s$ site in $\mathrm{KCl}:M^{2+}$, which constitutes an important feature of the Maxwell-Boltzmann distribution of the $M^{2+}-K^{+}$ vacancy pairs, is of fundamental importance in the understanding of numerous phenomena in polar crystals.