Extending density functional theory with near chemical accuracy beyond pure water

DFT simulations may be inaccurate in modeling aqueous systems, with results depending on the choice of the exchange-correlation functional. Here, the authors present an integrative method called HF-r(2)SCAN-DC4 that provides near chemical accuracy in electronic structure information not only for pure water but also for molecules dissolved in it Density functional simulations of condensed phase water are typically inaccurate, due to the inaccuracies of approximate functionals. A recent breakthrough showed that the SCAN approximation can yield chemical accuracy for pure water in all its phases, but only when its density is corrected. This is a crucial step toward first-principles biosimulations. However, weak dispersion forces are ubiquitous and play a key role in noncovalent interactions among biomolecules, but are not included in the new approach. Moreover, naive inclusion of dispersion in HF-SCAN ruins its high accuracy for pure water. Here we show that systematic application of the principles of density-corrected DFT yields a functional (HF-r(2)SCAN-DC4) which recovers and not only improves over HF-SCAN for pure water, but also captures vital noncovalent interactions in biomolecules, making it suitable for simulations of solutions.