Ab initio and DFT studies for accurate description of van der Waals interaction between rare‐gas atoms

To evaluate the accuracy of density functional theory (DFT) for describing van der Waals interaction between rare‐gas atoms, we performed coupled‐cluster theory restricted to single, double, and noniterative triple excitations [CCSD(T)], fourth‐order perturbation theory including single, double, and quadruple substitutions [MP4(SDQ)], and several DFT calculations for He, Ne, Ar, and Kr dimers. The results clarified that (1) CCSD(T) and MP4(SDQ) with an “adjusted” diffuse basis‐set reproduce the experimental trend in binding energies as well as equilibrium distances of these dimers, (2) MP3 and MP2 underestimate the binding energies, (3) Becke's three‐parameter exchange functional and the gradient‐corrected functional of Lee, Yang, and Paar (B3LYP) and B3PW91 completely fail to describe the binding, and (4) Perdew–Wang exchange‐correlation functional (PW91PW91) and its modified ones (MPWPW91 and MPW1PW91) can provide the binding states, although the calculated binding energies cannot reproduce the experimental trend in binding energies. Therefore, we conclude that the above DFT functionals cannot quantitatively describe the van der Waals interaction between rare‐gas atoms and that the Perdew‐Wang–type exchange functional needs further improvement to describe the interaction.