First-principles realization of a van der Waals–Maxwell theory for water

We generalize the van der Waals–Maxwell description of the fluid phase diagram to account for chemical specificities of polar molecular fluids such as hydrogen bonding in water. The theory is based on the reference interaction site model (RISM) integral equation method in the partially linearized hypernetted chain (PLHNC) approximation. The predictions for the liquid–vapor coexistence of water are in qualitative agreement with molecular simulations. The theory can be extended to electrolyte as well as non-electrolyte solutions, and to ionic liquids.