A reasonable candidate for the McMillan–Mayer ion–ion potential of strong 1–1 electrolytes

Abstract

It is assumed that the McMillan–Mayer ion–ion potential can be approximated by the sum of (i) a coulombic term, (ii) an exponentially damped oscillatory term and (iii) a further contribution which can have different functional expressions containing unknown parameters. A simultaneous best fit of the excess free energies of the most typical alkali-metal halides shows that the most reliable results are obtained when the last contribution has exponentially damped behaviour and the damping factors are specific to each pair of ions.

One finds that two sets of parameter values give equally satisfactory results even after having obtained the best fits to the heats of dilution and the excess volumes. However, analogy with the corresponding potentials in the gas phase makes one of the aforesaid sets of values more likely.