Fig. 1: 2B energies of the water hexamer isomers.

Two-body energies calculated for the first eight low-energy isomers of the water hexamer using SCAN, DC-SCAN, SCAN0 (with 25% exact exchange), and DC-SCAN0, along with the corresponding CCSD(T)/CBS reference values from ref. 78. The 2-body energy, on average, contributes ~80−85% to the total interaction energy in water14. The errors associated with a given functional relative to the CCSD(T)/CBS values are roughly the same for each isomer.