On ‘basic’ radii of simple and complex ions and the repulsion energy of ionic crystals

Abstract

This paper proposes a method in which minimization criteria are employed, within the framework of the Huggins and Mayer method for the calculation of repulsion energy in ionic crystals, to establish ‘basic’ radii for both simple and complex spherical ions. With radii so generated repulsion energies (and hence total lattice energies) can be obtained for salts containing spherical ions. The paper initially establishes ‘basic’ radii for alkali metal and halide ions using more recent data than those used originally by Huggins. A description is then given of how we propose to employ the method for salts having spherical complex ions. The examples of potassium, rubidium, caesium, thallium and ammonium hexachloroplatinates are chosen and values for ∆ H f Ɵ (PtCl 2¯ 6 ) (g) and ∆ H Ɵ hyd (PtCl 2¯ 6 ) (g) are assigned on the basis of the repulsion, and hence the total lattice potential, energies calculated for these five salts. Recent suspicions regarding the accuracy and reliability of the repulsion energy calculations for potassium hexachloroplatinate described in the current literature are re-examined and found to be justified.