Sammendrag
We present a detailed assessment of state-of-the-art exchange-correlation functionals. The assessment is carried out by comparing potential energy curves of van der Waals complexes of sodium and benzene calculated with density functional theory to extrapolated CCSD(T)/aug-cc-pVQZ values. According to the presented results, the Perdew-Burke-Ernzerhof functional (PBE) displays the best performance among the tested density functionals. PBE is the most accurate functional for the complexes studied, both in terms of absolute and relative accuracy.