Transferability of local density assisted implicit solvation models for homogeneous fluid mixtures*

Dependency on density or concentration of the state chosen during parametrization leads to low transferability in density/concentration space in bottom-up coarse graining.
For fluid phase equilibria the application of local density potentials appears a promising approach to overcome this shortcoming, as shown in previous work by Sanyal and Shell [J. Phys. Chem. B, 2018, 122, 5678].
Here, we want to further explore this method and test its ability to model solutions of methanol and water.
We find that a water-water LD potential improves the transferability of an implicit-methanol CG model towards high water concentration. Conversely, a methanol-methanol LD potential does not significantly improve the transferability of an implicit-water CG model towards high methanol concentration. These differences appear due to the presence of cooperative interactions in water at high concentrations that the LD potentials can capture. In addition, we formally demonstrate the analytical and numerical assumptions under these relative entropy optimization and the Inverse Monte Carlo method yield equivalent results.