Total Energy Method from Many-Body Formulation

The fruitfulness of traditional many-body Green's function theory for calculating the total energy of real systems is demonstrated using the random phase approximation in the Luttinger-Ward formulation. As the first application to a real system, the total energy of ${\mathrm{H}}_2$ is calculated as a function of nuclear separation and compared with the configuration interaction and the local density approximation results. While the local density result is in large error for large separations, the present approach gives satisfactory agreement with the configuration interaction results. The method is promising as an alternative to the quantum Monte Carlo technique.