Density Functional Theory based codes evaluate quite successfully intramolecular forces responsible of the atomic bonding. Within this technique one is able to obtain molecular relaxed structures that match almost perfectly the experimentally measured geometry. This is particularly true for very diluted single molecule structures in which the intermolecular interactions are almost negligible.
My question arises regarding the non-covalent intermolecular interactions appearing in molecular solids (Hydrogen bonding, ion-dipole forces, dipolar (and quadrupolar) interaction, van der Waals interaction, London forces, among others).
What is the correct formulation of DFT to include such forces in the calculation thus producing an adequate result in structural modeling of new molecular materials?