Solvation free-energy pressure corrections in the Three Dimensional Reference Interaction Site Model

TL;DR

This paper derives and validates pressure correction methods for improving solvation free energy predictions in the 3D-RISM model, aligning it with molecular density functional theory accuracy.

Contribution

It provides a rigorous derivation of pressure corrections for 3D-RISM, improving the accuracy of solvation free energy calculations.

Findings

Pressure corrections significantly improve 3D-RISM predictions.

The derived corrections align 3D-RISM results with MDFT.

Correct pressure expressions remove previous discrepancies.

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 recent 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.