Density-Corrected Many-body Representations in Aqueous Phase Chemistry

Kohn-Sham density functional theory (DFT) provides an unsatisfactory description of molecular interactions in solution, where local and non-local many-body (MB) effects compete. Density-corrected DFT (DC-DFT) has resurfaced as a practical approach for accurate energies of weakly interacting systems, often misrepresented by DFT. Herein, we discuss density-corrected molecular simulation, focusing on water and ion hydration, within a general framework that combines the ansatz of the many-body expansion with DC-DFT. We show that this framework, MB-DFT(DC), accurately describes molecular interactions in aqueous systems from the dimer to the condensed phase. We analyze the individual and collective effects of density-driven errors on the description of liquid water for several functionals, and identify when density-corrected potentials should be used. We explore the predictive capability of DC-SCAN and the MB-SCAN(DC) potential, showing that our density-corrected many-body approach predicts the N-body energies of hydrated ion clusters, discerning between ion--water/water--water interactions, with size-consistency and minimal loss of accuracy relative to coupled cluster. We provide insight from simulation into how density-correction translates to accurate descriptions of the structural properties of ions and water in the condensed phase, using the MB-SCAN(DC) potential. This connection between DC-DFT with a physics-based many-body treatment of molecular interactions, provides a promising path toward efficient DFT-based simulations with chemical accuracy.