Loos, Pierre-FrancoisTognetti, Vincent2018-11-292018-11-290021-9606http://hdl.handle.net/1885/152314Natural orbitals (NOs) are central constituents for evaluating correlation energies through efficient approximations. Here, we report the closed-form expression of the NOs of two-electron quantum rings, which are prototypical finite-extension systems and new starting points for the development of exchange-correlation functionals in density functional theory. We also show that the natural occupation numbers for these two-electron paradigms are in general non-vanishing and follow the same power law decay as atomic and molecular two-electron systems. C 2016 AIP Publishing LLC.application/pdf201610.1063/1.49409192018-11-29