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Fraenkel D. Computing excess functions of ionic solutions: the smaller-ion shell model versus the primitive model. 1. Activity coefficients. J Chem Theory Comput. 2015;11(1):178-92doi: 10.1021/ct5006938.
Fraenkel, D. (2015). Computing excess functions of ionic solutions: the smaller-ion shell model versus the primitive model. 1. Activity coefficients. Journal of chemical theory and computation, 11(1), 178-92. https://doi.org/10.1021/ct5006938
Fraenkel, Dan. "Computing excess functions of ionic solutions: the smaller-ion shell model versus the primitive model. 1. Activity coefficients." Journal of chemical theory and computation vol. 11,1 (2015): 178-92. doi: https://doi.org/10.1021/ct5006938
Fraenkel D. Computing excess functions of ionic solutions: the smaller-ion shell model versus the primitive model. 1. Activity coefficients. J Chem Theory Comput. 2015 Jan 13;11(1):178-92. doi: 10.1021/ct5006938. PMID: 26574216.
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J Chem Theory Comput. 2015 Jan 13;11(1):178-92. doi: 10.1021/ct5006938.

Computing excess functions of ionic solutions: the smaller-ion shell model versus the primitive model. 1. Activity coefficients.

Journal of chemical theory and computation

Dan Fraenkel

Affiliations

  1. Eltron Research & Development Inc., 4600 Nautilus Court South, Boulder, Colorado 80301-3241, United States.

PMID: 26574216 DOI: 10.1021/ct5006938

Abstract

The present study compares the Monte Carlo (MC) simulation of the primitive model (PM) ( Abbas, Z. et al. J. Phys. Chem. B 2009 , 113 , 5905 ), by which activity coefficients of many binary ionic solutions have been computed through adjusting ion-size parameters (ISPs) for achieving best fit with experiment, with a parallel fit and ISP adjustment, employing the Smaller-ion Shell (SiS) treatment ( Fraenkel, D. Mol. Phys. 2010 , 108 , 1435 ), a Debye-Hückel type theory ("DH-SiS") considering counterions of unequal size. DH-SiS is analogous to the unrestricted PM (UPM), so the comparison is with the MC simulation of the UPM, "MC-UPM". Among the representative electrolytes NaCl, KCl, NaClO4, CaCl2, Ca(ClO4)2, and LaCl3, in water at 25 °C, the 1-1 electrolytes exhibit a far better fit quality for DH-SiS than for MC-UPM, and the fit extends to higher concentration. Moreover, theoretical single-ion activity coefficients derived from DH-SiS agree with experimental estimation for solutions of NaCl, CaCl2, and other electrolytes ( Fraenkel, D. J. Phys. Chem. B 2012 , 116 , 3603 ), whereas parallel MC-UPM predictions are at odds with experiment. Additional advantages of DH-SiS over MC-UPM are in (a) employing co-ion ISPs that are usually equal to the crystallographic ion diameters and (b) easily applying ISP nonadditivity in adjusting counterion ISPs.

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