  We propose a new method for calculating total energies of systems of
interacting electrons, which requires little more computational resources than
standard density-functional theories. The total energy is calculated within the
framework of many-body perturbation theory by using an efficient model of the
self-energy, that nevertheless retains the main features of the exact operator.
The method shows promising performance when tested against quantum Monte Carlo
results for the linear response of the homogeneous electron gas and structural
properties of bulk silicon.

Condensed Matter