Calculation of the free energy of solvation and dissociation of HCl in water via Monte Carlo simulations and continuum solvation models

McGrath, M. J.; Kuo, I.-F. W.; Ngouana, B. F.; Ghogumo, J. N.; Mundy, C. J.; Marenich, A. V.; Cramer, C. J.; Truhlar, D. G.; Siepmann, J. I.
Phys. Chem. Chem. Phys. 2013, 15, 13578 (doi:10.1039/c3cp51762d).

The Gibbs free energy of solvation and dissociation of hydrogen chloride in water is calculated through a combined molecular simulation/quantum chemical approach at four temperatures between T = 300 and 450 K. The Gibbs free energy is first decomposed into the sum of two components: the Gibbs free energy of transfer of molecular HCl from the vapor to the aqueous liquid phase and the standard-state Gibbs free energy of acid dissociation of HCl in aqueous solution. The former quantity is calculated using Gibbs ensemble Monte Carlo simulations using either Kohn-Sham density functional theory or a molecular mechanics force field to determine the system's potential energy. The latter Gibbs free energy contribution is computed using a continuum solvation model utilizing either experimental reference data or micro-solvated clusters. The predicted combined solvation and dissociation Gibbs free energies agree very well with available experimental data.