Møller-Plesset Adiabatic Connection Theory for Diverse Noncovalent Interactions

Møller–Plesset adiabatic connection (MPAC) theory provides a powerful framework for constructing approximations to wavefunction-based correlation energy, enabling modeling of non- covalent 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 oper- ate 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 perfor- mance, we introduce MPAC25, a simple two-parameter functional treating neutral and charged NCIs equally, as demonstrated on DES15K benchmarks. Overall, MPAC functionals effec- tively describe a wide range of NCIs, including those beyond the reach of other methods, rep- resenting a significant step toward predictive simulations of molecular interactions in complex environments and motivating further MPAC developments.