Stated as exact by the Hohenberg-Kohn Theorems, density-functional theory (DFT) is in practice ruled by the approximation of the exchange-correlation energy term. Five main classes of approximations were established for this term, all of them ranked according to their level of nonlocality in the so-called Perdew’s Ladder.

In the density-functional landscape of approximations, two main schools of thinking coexist. The first one works on complex functionals of the density introducing deliberately empiricism by training parameters versus reference chemical databases, while the second develops simple density functional expressions ruled by physical assumptions and minimizing or avoiding empiricism. The collaborative research performed here by ITODYS (Université de Paris), the chemical-physics department of the University of Alicante (Spain), and i-CLeHS (Chimie ParisTech) is part of the latter school of thinking and develops a new and simple route to derive range-separated exchange hybrid and double hybrid density functionals in a nonempirical fashion.

This research published in J. Chem. Phys is selected as an Editor’s Pick and is part of the the JCP Emerging Investigators Special Collection.