Representability and Transferability of Kirkwood–Buff Iterative Boltzmann Inversion Models for Multicomponent Aqueous Systems

Abstract

We discuss the application of the Kirkwood–Buff iterative Boltzmann inversion (KB-IBI) method for molecular coarse-graining (Ganguly et al.<i> J. Chem. Theory Comput.</i> <b>2012</b>, <i>8</i>, 1802) to multicomponent aqueous mixtures. Using a fixed set of effective single-site solvent–solvent potentials previously derived for binary urea–water systems, solute–solvent and solute–solute KB-IBI coarse-grained (CG) potentials have been derived for benzene in urea–water mixtures. Preferential solvation and salting-in coefficients of benzene are reproduced in quantitative agreement with the atomistic force field model. The transferability of the CG models is discussed, and it is shown that free energies of formation of hydrophobic benzene clusters obtained from simulations with the CG model are in good agreement with results obtained from all-atom simulations. The state-point representability of the CG models is discussed with respect to reproducing thermodynamic quantities such as pressure, isothermal compressibility, and preferential solvation. Combined use of KB-IBI and pressure corrections in deriving single-site CG models for pure-water, binary mixtures of urea and water, and ternary mixtures of benzene in urea–water at infinite benzene dilution provides an improved scheme to representing the atomistic pressure and the preferential solvation between the solution components. It is also found that the application of KB-IBI leads to a faster and improved convergence of the pressure and potential energy compared to the IBI method