Improving Density Functional Theory for weakly bonded systems via the Møller-Plesset Adiabatic Connection

Non-covalent interactions (NCIs) play a crucial role in biology, chemistry, material science, and everything in between. To improve pure quantum chemical simulations of NCIs, we propose a methodology [1,2] for constructing approximate correlation energies via an interpolation along the Møller adiabatic connection (MP AC) [3,4]. These interpolations approximate the correlation energy, by recovering MP2 at small coupling strengths and having the correct large-coupling strength expansion of the MP AC, recently shown to be a functionals of the Hartree-Fock density [3][4]. In the newest generation of these interpolation functionals, regularization and spin-scaling strategies were applied to MP2 correlation energies, which fixes some of the known issues of MP2 and also decreases its computational cost. This combination yields c_osκ_os-SPL2, which exhibits superior accuracy for NCIs compared to any of the individual strategies. With the N⁴ formal scaling, c_osκ_os-SPL2, is competitive or often outperforms more expensive dispersion- corrected double hybrids for NCIs. The accuracy of c_osκ_os-SPL2 particularly shines for anionic halogen bonded complexes, where it surpasses standard dispersion-corrected DFT by a factor of 3 to 5. If time allows it, new results will be presented instead.