  We carried out numerical calculations by an extended-Hueckel program in order
to check the analytical results reported in the preceding Part I and Part II.
We typically consider alkali halide clusters composed of some tens of
constituent atoms to calculate electronic energies under static conditions or
versus the displacements of particular atoms. Among other things, the
off-center displacement of substitutional Li+ impurity in most alkali halides
is evidenced. The trigonometric profile of the rotational barriers is also
confirmed for KCl.
