How Does HF-DFT Achieve Chemical Accuracy for Water Clusters?

• DOI: 10.1021/acs.jctc.4c00560
• Publication Date: 2024-06-28T05:48:52Z
• Authors: Aaron D. Kaplan; Chandra Shahi; Raj K. Sah; Pradeep Bhetwal; Bikash Kanungo; Vikram Gavini; John P. Perdew
• Keywords: Water dimer

Bolstered by recent calculations of exact functional-driven errors (FEs) and density-driven (DEs) semilocal density functionals in the water dimer binding energy [Kanungo, B. J. Phys. Chem. Lett. 2024, 15, 323–328], we investigate approximate FEs DEs neutral clusters containing up to 20 monomers, charged clusters, alkali- halide-water clusters. Our proxy for is r2SCAN 50, a 50% global hybrid exchange with r2SCAN, which may be less correct than compact monomer but importantly more long-range electron transfers noncompact We show that SCAN makes substantially larger while both make essentially same DEs. Unlike case barrier heights, these are small relative sense become large an absolute only due increase cluster size. SCAN@HF, short evaluated on Hartree–Fock (HF) density, produces cancellation it chemically accurate predicting energies Likewise, adding dispersion correction r2SCAN@HF, as composite method HF-r2SCAN-DC4, its FE negative permitting near-perfect DE. itself (and even so, 50 density), almost perfect differences between hexamers, thus probably also liquid away from boiling point. Thus, accuracy methods like SCAN@HF HF-r2SCAN-DC4 not HF being closer compensation greater degree localization. give argument reliability this unconventional error diverse molecular properties. Finally, confirm description trimer via Kohn–Sham inversion CCSD(T) density.