Ionic potential models in insulators having the rutile structure

It is shown that the observed crystal symmetry, lattice parameters, and vibrational properties of insulators that crystallize in the rutile structure must be considered together in order to construct credible interionic potential models for these materials. Illustrative results are presented for ${\mathrm{TiO}}_2$ and ${\mathrm{MnF}}_2$, and for comparison, several alkali halides. Potential models used in recent defect studies in ${\mathrm{TiO}}_2$ do not predict the correct crystal structure.