Many-body effects on one-electron energies and wave functions in low-dimensional systems

We have studied the quasiparticle (QP) wave functions and energies of the GaAs(1 1 0) surface and of the cluster Na-4 within Hedin\textquoterights GW approximation. We found that the commonly accepted assumption that the Density Functional Theory (DFT)-Local Density Approximation (LDA) wave functions are a very good approximation for the true QP ones can be wrong. We analyze the effect of the resulting changes in the wave functions on the optical spectra. (C) 2001 Elsevier Science B.V. All rights reserved.