Møller-Plesset Adiabatic Connection Theory for Diverse Noncovalent Interactions.

Møller-Plesset adiabatic connection (MPAC) theory provides a powerful framework for constructing approximations to wave function-based correlation energy, enabling modeling of noncovalent interactions (NCIs) with near-CCSD(T) accuracy. We show that approximate MPAC functionals consistently outperform MP2 and dispersion-corrected DFT (DFT+DISP) across diverse systems, including charged and charge-transfer complexes. MPAC functionals operate holistically at the electronic level, require no heuristic dispersion corrections, and achieve near-chemical accuracy even for abnormal NCIs, cases where DFT+DISP errors exceed those of DFT. To further improve MPAC for abnormal cases without compromising overall performance, we introduce MPAC25, a simple two-parameter functional treating neutral and charged NCIs equally, as demonstrated on DES15K benchmarks. Overall, MPAC functionals effectively describe a wide range of NCIs, including those beyond the reach of other methods, representing a significant step toward predictive simulations of molecular interactions in complex environments and motivating further MPAC developments.