New theoretical method for rapid prediction of solvation free energy in water.

We present a new theoretical method for rapid calculation of the solvation free energy in water by combining molecular simulation and the classical density functional theory (DFT). The DFT calculation is based on an accurate free-energy functional for water that incorporates the simulation results for long-range correlations and the fundamental measure theory for the molecular excluded-volume effects. The numerical performance of the theoretical method has been validated with simulation results and experimental data for the solvation free energies of halide (F(-), Cl(-), Br(-), and I(-)) and alkali (Li(+), Na(+), K(+), Rb(+), and Cs(+)) ions in water at ambient conditions. Because simulation is applied only to the particular thermodynamic condition of interest, the hybrid method is computationally much more efficient than conventional ways of solvation free energy calculations.