Correction terms for the solvation free energy functional of three-dimensional reference interaction site model based on the reference-modified density functional theory

Abstract

Recently, we derived the reference-modified density functional theory (RMDFT) to calculate the solvation free energy (SFE) with high accuracy, introducing a reference system to the DFT for polyatomic molecular liquids. The RMDFT functional consists of the DFT using second-order approximation (DFT(D)) functional and the correction terms. The DFT(D) functional are equivalent to the Singer-Chandler formula for the hypernetted chain closure equation. The contribution of the correction terms has a strong correlation with the partial molar volume (PMV) of solute. Thus, the RMDFT functional has almost the same accuracy as the PMV correction. Furthermore, we combined the Singer-Chandler formula for the Kovalenko-Hirata closure and the correction terms to avoid inconsistency between the closure equation and the SFE functional. It become clear that the inconsistency is unimportant, whereas the combined functional works well for the amino acid side chain analogues molecules.