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3018200 
Journal Article 
Computing Excess Functions of Ionic Solutions: The Smaller-Ion Shell Model versus the Primitive Model. 2. Ion-Size Parameters 
Fraenkel, Dan 
2015 
Yes 
Journal of Chemical Theory and Computation
ISSN: 1549-9618
EISSN: 1549-9626 
11 
1 
193-204 
26574217 
WOS:000348085400022 
A recent Monte Carlo (MC) simulation study of the primitive model (PM) of ionic solutions (Abbas, Z. et al. J. Phys. Chem. B 2009, 113, 5905) has resulted in an extensive mapping of real aqueous solutions of 1-1, 2-1, and 3-1 binary electrolytes and a list of recommended ionic radii for many ions. For the smaller cations, the model-experiment fitting process gave much larger radii than the respective crystallographic radii, and those cations were therefore claimed to be hydrated. In Part 1 (DOI 10.1021/ct5006938) of the present work, the above study for the unrestricted PM - dubbed MC-UPM - has been confronted with the Smaller-ion Shell (SiS) treatment (Fraenkel, D. Mol. Phys. 2010, 108, 1435), or DH-SiS, by comparing the range and quality of model-experiment fits of the mean ionic activity coefficient as a function of ionic concentration. Here I compare the ion-size parameters (ISPs) of best fit of the two models and argue that since ISPs derived from DH-SiS are identical with (or close to) crystallographic or thermochemical ionic diameters for both cations and anions, and they do not depend on the counterion - they are more reliable, as physicochemical entities, than the PM-derived recommended ionic radii.