A Theoretical Study of Simple Complexes of Point Defects in Alkali Halides by the Lattice Static Method

Abstract

Expressions are obtained for the energ-of alkali halide crystals with two kinds of simple complexes of point defects -divalent impurity with vacancy and bivacancy -using the lattice static method. The heat of solution of Mg2+, Ca2+, Sr2+, and Ba2+ in NaCl, KCl, and KBr is calculated. Numerical calculations show that in some cases the nearest-neighbour complex is less stable than the next-nearest-neighbour complex. The formation energy of a bivacancy is calculated in the same crystals. The results are consistent with those obtained experimentally. It is shown that in the latter case the configuration of the nearest-neighbour complex is the most stable one.

A Theoretical Study of Diffuse Scattering by Clusters in Alkali Halides

“…Particularly, by the Mott-Littleton method [8] it was shown that in the case of the M2+-V dipole, both configurations of nearest neighbours and next nearest neighbours can take place, the latter is realized in the case of impurities with small radius of the ions. Analogous results have been obtained in [9] using the method of lattice statics.…”

“…Mutual compensation of Coulomb and short-range forces acting on the lattice from the dipole-located in various sublattices (divacancy), also influenes the energy of the lattice relaxation caused by the dipole, which is always less than the corresponding energy for the dipole, located in one sublattice (M2+-V) [9]. However, if the cross-section of the Huang scattering differs by one order, the difference in the energy relaxation is significantly less, since this compensation completely shows itself at great distances from the defect, while the relaxation energy is, in the first place, determined by the nearest vicinity of the defect.…”

“…; force P,(Q) influencing the v crystal sublattice from the defect, can be obtained by the method described in [9]. However, it is easier to write it in the form which is a generalization of the results obtained in [9], using a superposition principle. The complete Ewald form with a parameter q is given as where d is the lattice parameter and k the vector of the reciprocal lattice.…”