Change in density of NaCl:KCl crystal with Br impurities

The Dick and Das theory is revised in detail. We found that the errors in the repulsive energy expression and also for the Van der Waals energy are very important when the lattice deformation around a Br impurity is calculated. The right expressions obtained were used in order to obtain the displacements of the first and second neighbors around the impurity. The changes in density of the NaCl:KCl crystal obtained from these displacements are very large. The conclusion of this work is that the expressions given by Dick and Das are wrong (their formulas have not simple print errors) (Author)