Nonempirical Adiabatic Connection Correlation Functional from Hartree–Fock Orbitals

We present a nonempirical strategy to construct a correlation functional rooted in the Møller-Plesset (MP) adiabatic connection (AC) formalism for the strong-interaction regime, which satisfies both the weak- and strong-interaction limits and describes accurately the uniform electron gas (UEG) model. The functional is based on Hartree-Fock (HF) orbitals and employs only the UEG and helium atom as model systems; thus, it can be considered a nonempirical and nonlinear generalization of post-HF approaches based on the second-order perturbation theory (MP2) correlation. The functional describes the correlation of atoms with 1 mHa/electron accuracy, and it is also accurate for jellium surface energies. Accurate tests using a nearly complete basis set on diverse systems and properties (atomization/interaction energies, dispersion forces, and ionization potentials) have shown an excellent performance of the functional that corrects the MP2 overbinding without error cancellation. The present investigation can open the way for the development of a new generation of post-HF functionals based on nonlinear MP2 contributions and strong-correlation ingredients.