Thermodynamic state-dependent structure-based coarse-graining of confined water.

We develop thermodynamic state-dependent single-site isotropic coarse-grained potentials to predict the structure of water confined inside graphene slit-like channels by two multiscale simulation approaches: the coarse-grained molecular dynamics (CG-MD) and the empirical potential-based quasi-continuum theory (EQT). The structurally-consistent coarse-grained potentials for the CG-MD and EQT are systematically determined from the reference all-atom SPC/E water MD (AA-MD) results. For optimization of the CG-MD potentials, the relative entropy based coarse-graining method is used, and for determination of the EQT potentials, we develop a potential of mean force matching scheme. The optimized coarse-grained potentials are found to be dependent on the thermodynamic state. They are evaluated for their ability to predict the density profile of confined water, and it is found that the results obtained by the CG-MD and EQT simulations are in good agreement with the reference AA-MD results.