Assessing the accuracy of exchange-correlation functionals in density functional theory for hydrogen-benzene and hydrogen-hydrogen interactions

We calculated the interaction energies of hydrogen-benzene and hydrogen-hydrogen complexes using dispersion-inclusive exchange-correlation functionals in density functional theory and compared them with results from the coupled cluster method with single, double, and perturbative triple excitations and those from the adiabatic-connection fluctuation-dissipation theorem within the random phase approximation. For both complexes, the recent generations of nonlocal van der Waals density functionals show overall improvement over semilocal exchange-correlation functionals with dispersion corrections, yielding good agreement with the coupled cluster method. We discuss their accuracy and recommend suitable exchange-correlation functionals based on different evaluation metrics.