Range separation combined with the Overhauser model: Application to the H₂ molecule along the dissociation curve

The combination of density-functional theory with other approaches to the many-electron problem through the separation of the electron-electron interaction into a short-range and a long-range contribution (range separation) is a successful strategy, which is raising more and more interest in recent years. We focus here on a range-separated method in which only the short-range correlation energy needs to be approximated, and we model it within the "extended Overhauser approach". We consider the paradigmatic case of the H$_2$ molecule along the dissociation curve, finding encouraging results. By means of very accurate variational wavefunctions, we also study how the effective electron-electron interaction appearing in the Overhauser model should be in order to yield the exact correlation energy for standard Kohn-Sham density functional theory.