Abstract
A recently proposed double-hybrid functional called XYG3 and a semilocal GGA
functional (B97-D) with a semiempirical correction for van der Waals interactions have been
applied to study the potential energy curves along the dissociation coordinates of weakly bound
pairs of molecules governed by London dispersion and induced dipole forces. Molecules treated
in this work were the parallel sandwich, T-shaped, and parallel-displaced benzene dimer, (C6H6)2;
hydrogen sulfide and benzene, H2S·C6H6; methane and benzene, CH4 ·C6H6; the methane dimer,
(CH4)2; and the pyridine dimer, (C5H5N)2. We compared the potential energy curves of these
functionals with previously published benchmarks at the coupled cluster singles, doubles, and
perturbative triplets [CCSD(T)] complete-basis-set limit. Both functionals, XYG3 and B97-D,
exhibited very good performance, reproducing accurate energies for equilibrium distances and
a smooth behavior along the dissociation coordinate. Overall, we found an agreement within a
few tenths of one kcal mol-1 with the CCSD(T) results across the potential energy curves.
