Accurate total energies without self-consistency - art. no. 226401

We present a new way of calculating approximate but accurate total energies within the framework of density functional theory. Our technique is based on an expansion of the energy functional to second order and does not requi re self-consistent iterations of the total density. The functional can be m inimized by using the same techniques as developed for variational density functional perturbation theory. The method is ideally suited to systems com posed of weakly interacting fragments, but it can also be applied to semico nductors and insulators. We show the versatility of our approach in a varie ty of examples exhibiting different types of chemical bonding.