A density functional approach for ab initio calculations in the presence of a solvent

The study of a system in contact with liquid water typically involves a large number of atoms and averaging over a large number of configurations, making ab initio study of such systems prohibitive. This talk presents a formally exact way to circumvent this problem by separating the free energy of the system into three parts: a Kohn-Sham theory for the solute electron density, a classical density functional theory for the water molecular density, and a free energy of interaction between these two systems. We shall present various approximations for the interaction functional within this new joint density functional theory (JDFT) framework.