23, 24, 25, 26 Standard DFT calculations are performed self-consistently (SC). 19, 20, 21, 22 In addition to being a rigorous exact theory, DC-DFT gives practical guidance on when and how it can be used to reduce errors in DFT simulation. For more details, see the main text and supplementary information.ĭC-DFT is a general framework that separates errors of any self-consistent DFT calculations into a contribution coming from the approximate D (density) and the true error coming from the approximate F (functional). One cluster, H 3O +(H 2O) 6OH − (at x close to 4 kcal/mol) is an outlier argued to exhibit a significant multiconfigurational character 4 d relative energies of water 20-mer isomers (not density sensitive) from WATER27, where self-consistent SC-r 2SCAN-D4 performs best, but using the HF density introduces little error e errors in interaction energies in the water ⋯ aspirin dimer structures from an MD simulation at T = 298.15 K f mean-absolute-errors (MAEs) for intra- and inter-molecular noncovalent interactions datasets from the GMTKN55 database. a the interaction energy of various configurations of the stacked cytosine dimer, where HF-SCAN underbinds by 2–3 kcal/mol b energies of water hexamer relative to the lowest-lying prism isomer, with HF-SCAN underestimating by up to 1 kcal/mol c errors in binding energy of WATER27 complexes as a function of density sensitivity (how much a DFT energy changes when the density is changed), showing how large errors can be without using the HF density. Figure 1 shows how an integratively designed DC-DFT procedure, HF-r 2SCAN-DC4, describes not only the interactions between water-water, water-organic molecules, and water-biochemical molecules in various situations, but also the interactions of noncovalent complexes at chemical accuracy or better.Ītom color code: C, gray O, red N, blue and H, white. For this reason, a complete understanding of the reaction is possible only when the interaction between water and other molecules is accurately described. 3, 4 The role of water in a chemical or biochemical reaction goes beyond providing an environment to help a reaction in an aqueous solvation and is often explicitly involved in the mechanism. showed that the strongly constrained and appropriately normed (SCAN) functional, when used in tandem with density-corrected DFT (DC-DFT), is a game changer for water simulation, because it brings KS-DFT close to chemical accuracy. 15, 16, 17, 18Ī recent breakthrough in this direction by Dasgupta et al. 10, 11, 12, 13, 14 But, despite an excellent accuracy to cost ratio, historically KS-DFT has been unable to deliver sufficiently high accuracy in water simulations to reproduce experimental data. 2, 3, 4, 5, 6, 7, 8, 9 As ab initio quantum-chemical methods are too expensive for large systems, Kohn-Sham density functional theory (KS-DFT) has become a workhorse of electronic structure methods for running water calculations. 1 Given the vital importance of water in fields that vary from material science to biology, there has been a recent surge in the development and competition of different electronic structure methods for simulating water. The properties of water, such as the uniqueness of its phase diagram, never stop surprising scientific communities.
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