Title: Thermodynamics of primitive model electrolytes in the symmetric and modified Poisson-Boltzmann theories. A comparative study with Monte Carlo simulations
Author(s):

	A.O. Quiñones (Laboratory of Theoretical Physics, Department of Physics, University of Puerto Rico, 17 Avenida Universidad, STE 1701, San Juan, Puerto Rico 00925-2537, USA) ,
	L.B. Bhuiyan (Laboratory of Theoretical Physics, Department of Physics, University of Puerto Rico, 17 Avenida Universidad, STE 1701, San Juan, Puerto Rico 00925-2537, USA) ,
	C.W. Outhwaite (Department of Applied Mathematics, University of Sheffield, Sheffield S3 7RH, UK)

Osmotic coefficients, individual and mean activity coefficients of primitive model electrolyte solutions are computed at different molar concentrations using the symmetric Poisson-Boltzmann and modified Poisson-Boltzmann theories. The theoretical results are compared with an extensive series of Monte Carlo simulation data obtained by Abbas et al. [Fluid Phase Equilib., 2007, 260, 233; J. Phys. Chem. B, 2009, 113, 5905]. The agreement between modified Poisson-Boltzmann predictions with the "exact" simulation results is almost quantitative for monovalent salts, while being semi-quantitative or better for higher and multivalent salts. The symmetric Poisson-Boltzmann results, on the other hand, are very good for monovalent systems but tend to deviate at higher concentrations and/or for multi-valent systems. Some recent experimental values for activity coefficients of HCl solution (individual and mean activities) and NaCl solution (mean activity only) have also been compared with the symmetric and modified Poisson-Boltzmann theories, and with the Monte Carlo simulations.

Key words: electrolytes, primitive model, symmetric Poisson-Boltzmann theory, modified Poisson-Boltzmann theory, Monte Carlo simulations
PACS: 82.45.Fk, 61.20.Qg, 82.45.Gj

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