Density functional theory for molecular liquids based on interaction site model and self-consistent integral...

We propose a novel classical density functional theory (DFT) for inhomogeneous polyatomic liquids based on the grand canonical ensemble of a solute-solvent system. Different from the existing DFT for interaction site model developed by Chandler et al. [J. Chem. Phys. 85, 5971 (1986)], the fundamental quantities in the present theory are the radial density distributions around the atomic site of the solute molecule. With this development and the reference interaction site model equation, we provide self-consistent integral equations for calculating the site-site pair correlation function (PCF) and apply it to the structure of the Lennard-Jones dimer, HCl, and H₂O molecular fluids. The site-site PCFs obtained from the new scheme agree well with those from Monte Carlo simulation results.