An efficient, renormalized self-energy for calculating the electron binding energies of closed-shell molecules and anions

The energy-dependent, nonlocal correlation potential known as the self-energy that appears in the Dyson equation has a pole and residue structure that enables renormalizations of its low-order, perturbative contributions to be estimated. The partial third-order (P3) approximation has been extensively applied to the ionization energies of closed-shell, organic molecules and is the most successful example of a low-order, self-energy method. A renormalization based on the P3 self-energy estimates higher-order contributions by scaling low-order terms that chiefly describe final-state relaxation. The resulting P3+ self-energy retains the accuracy and efficiency of the P3 approximation, but also improves the latter method's performance with respect to the calculation of anion electron detachment energies without the introduction of adjustable parameters. An application to an anion that previously has yielded only to more intricate treatments of electron correlation demonstrates the power of this simple, new approximation. (c) 2005 Wiley Periodicals, Inc.