An Approach to Computing Solvent Reorganization Energy

A method for accurate calculation of reorganization free energy of an explicit solvent solvating a solute molecule is presented. The method relies on the knowledge of solvation free energy known either from experimental measurement or from accurate calculation. An important part of this approach lies in the calculation of entropy in solute-solvent interaction free energy using the interaction entropy method, combined with the calculation of enthalpy of solvent reorganization based on a finite number of solvent molecules near the solute molecule. This interaction entropy-solvent reorganization or IESR method enables one to compute both enthalpy and entropy components of the solvent reorganization energy from MD simulation of the solvated system. The calculated results are determined by the molecular force field only without any empirical parameter. The current method is applied to computing the reorganization energies of water solvent solvating a wide range of solute molecules including both hydrophilic and hydrophobic ones. The accuracy of the approach is indirectly verified by the excellent agreement of individual enthalpies and entropies of the solvation energies between theory and experiment.