Strong-coupling limit in Møller-Plesset theory:
Exact results and approximations to treat non-covalent interactions
Paola Gori Giorgi
I will illustrate our recent results on the large coupling-strength limit of the adiabatic connection (AC) that has as weak-interaction expansion the Møller-Plesset (MP) perturbation series. We find that in this limit the MP AC has an expansion in terms of functionals of the Hartree-Fock density with a clear physical meaning. Based on these findings, we introduce approximations for the MP AC built by interpolating between MP2 and this new large-coupling strength limit, which are size consistent for systems composed of fragments with a non-degenerate ground state. These functionals have the same cost as double hybrids and capture non-covalent interactions (NCI) very accurately, without using dispersion corrections, as will be shown with results for several NCI test sets (S66, CT7, NGD8, DI6 and L7) and dissociation curves ranging from small dimers of noble gases to larger benzene-pyridine dimers.