Soft matter and van der Waals interactions

The standard local (LDA) or semilocal (GGA) approximations to DFT do not account correctly for weak, nonlocal correlations, e.g. van der Waals interactions, which are important in "soft" or sparsely pckerd materials like polymers, biomolecules, liquid crystals,...

Lately, a generalized density functional that includes nonlocal correlations has been developed. When tested on graphite, it yields good agreement with experimental vaalues of the interplanar distance, as opposed to standard DFT, which gives no binding at all (see figure). To read more about this, look up Phys. Rev. B 62, 6997 (2001) by H. Rydberg, B. I. Lundqvist, D. Langreth, and M. Dion (or ask Per Hyldgaard for more information).