Analysis of Henry's constant for carbon dioxide in water via Monte Carlo simulation

We present calculations of the Henry constant for carbon dioxide in water by Monte Carlo simulations over a broad range of temperatures, from 0 ∘C to the critical temperature of water. A range of intermolecular potential models is examined for each species. Carbon dioxide is modelled by two three-site (EPM2, and Errington and Panagiotopoulos) potentials and water is modelled by four three-site (SPC, SPC/E, MSPC/E, and Errington and Panagiotopoulos) potentials, by the four-site TIP4P potential and by the five-site TIP5P potential. Henry's constant is computed via the Widom test-particle insertion method and by means of a staged free-energy perturbation method. The performance of the various potential models with respect to the accuracy of their prediction of the Henry constant is discussed. The staged free-energy perturbation method, employed at several representative temperatures, allows further analysis of the Henry constant with respect to the free energy of cavity formation for hosting the CO2 solute molecule in the H2O solvent and the free energy of interactions between the CO2 solute molecule and the H2O solvent. We found that all CO2/H2O models predicted a qualitatively correct temperature dependence of the Henry constant but only the Errington and Panagiotopoulos CO2/H2O model gave values for the Henry constant in reasonable agreement with experimental data.