second-order perturbation treatment of the electron correlations.
The dimer axis was oriented perpendicular to the benzene
ring to mimic the tipgraphene geometry. The
CASPT2 results corroborated the order Cu > Au≈Ag of
the interaction energies, confirming that the apparently
strong binding of copper is not an artifact of the
EEþvdW method. The different affinities of Cu, Ag, and