  An adiabatic-connection fluctuation-dissipation theorem approach based on a
range separation of electron-electron interactions is proposed. It involves a
rigorous combination of short-range density functional and long-range random
phase approximations. This method corrects several shortcomings of the standard
random phase approximation and it is particularly well suited for describing
weakly-bound van der Waals systems, as demonstrated on the challenging cases of
the dimers Be$_2$ and Ne$_2$.
