Ionic sizes and born repulsive parameters in the NaCl-type alkali halides—II

The procedure described in I for the determination of the crystal radii of the ions in the individual NaCl-type alkali halides from solid-state data by the Born model is applied, adopting a generalized Huggins-Mayer form for the Born repulsive energy (i.e. allowing the hardness parameter to vary from salt to salt). The resulting values of the crystal radii agree within 0·05 Å with the values obtained in I with the Huggins-Mayer and Pauling forms. This indicates that the Born model, irrespective of the specific plausible form adopted for the Born repulsive energy, leads to relative values of the crystal radii for the alkali and halogen ions in the NaCl structure exceeding by about 0·3 Å the traditional relative values, which refer to nearly free ions. Qualitative and quantitative evidence supporting these ionic deformations is discussed.