Self-interaction error of local density functionals for alkali–halide dissociation

We document the effect of self-interaction error in local density functionals for the dissociation of alkali–halide salts. The dissociated species have energies which are below the sums of atomic energies. There is a dramatic effect on the density itself, leaving unphysical partial charges on the atoms at dissociation. Unlike the cation-dimer paradigm, this manifestation of self interaction occurs in an overall neutral system with an even number of electrons. The reason why salts draw out this error is discussed in terms of electronegativity.