Solvation free-energy pressure corrections in the Three Dimensional Reference Interaction Site Model (1511.04475v1)

Abstract: Solvation free energies are efficiently predicted by molecular density functionnal theory (MDFT) if one corrects the overpressure introduced by the usual homogeneous reference fluid approximation. Sergiievskyi et al. [Sergiievskyi et al., JPCL, 2014, 5, 1935-1942] recently derived the rigorous compensation of this excess of pressure (PC) and proposed an empirical "ideal gas" supplementary correction (PC+) that further enhances the calculated solvation free energies. In a paper [Misin et al, JCP, 2015, 142, 091105], those corrections were applied to solvation free energy calculations using the three-dimensional reference interaction site model (3D-RISM). As for classical DFT, PC and PC+ corrections improve greatly the predictions of 3D-RISM, but PC+ is described as decreasing the accuracy. In this article, we first derive rigorously the PC and PC+ corrections for 3D-RISM. We show the reported discrepancy is then taken off by introducing the correct expression of the pressure in 3D-RISM. This provides a consistent way to correct the solvation free-energies calculated by 3D-RISM method.