Accuracy of Intermolecular interaction Energies, Particularly Those of Hetero Atom Containing Molecules Obtained by van der Waals DFT Calculations

The performance of 24 vdW-DF functionals were evaluated. The calculated intermolecular interaction potentials for 11 complexes, which conatain O, S, Se, N, P, F, Cl and Br atoms, were compared with CCSD(T)/CBS level potentials to evaluate their accuracy. The performance depends on the choice of vdW-functional significantly. The vdW-DF3-opt1 functional shows the best performance. The deviation ratios of calculated interaction energies of the complexes using the vdW-DF3-opt1 functional to CCSD(T) level interaction energies at the potential minima are -6 to 14 %. As a general tendency, the accuracy is improved in the order of vdW-DF, vdW-DF2, and vdW-DF3, but even if they belong to the same group, the accuracy greatly differs depending on each functional. The calculations of hydrocarbon molecules show better performance compared with heteroatom containing molecules in most cases. The calculations using the vdW-DF3-opt1 functional and the best dispersion corrected DFT calculations show nearly identical performance.