Europhys. Lett.
Volume 76, Number 2, October 2006
Page(s) 298 - 304
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 20 September 2006
Europhys. Lett., 76 (2), pp. 298-304 (2006)
DOI: 10.1209/epl/i2006-10266-6

Fully self-consistent GW calculations for atoms and molecules

A. Stan, N. E. Dahlen and R. van Leeuwen

Rijksuniversiteit Groningen, Materials Science Centre, Theoretical Chemistry Nijenborgh 4, 9747AG Groningen, The Netherlands

received 11 April 2006; accepted in final form 29 August 2006
published online 20 September 2006

We solve the Dyson equation for atoms and diatomic molecules within the GW approximation, in order to elucidate the effects of self-consistency on the total energies and ionization potentials. We find GW to produce accurate energy differences although the self-consistent total energies differ significantly from the exact values. Total energies obtained from the Luttinger-Ward functional $E_{\rm {LW}}[G]$ with simple, approximate Green functions as input, are shown to be in excellent agreement with the self-consistent results. This demonstrates that the Luttinger-Ward functional is a reliable method for testing the merits of different self-energy approximations without the need to solve the Dyson equation self-consistently. Self-consistent GW ionization potentials are calculated from the Extended Koopmans Theorem, and shown to be in good agreement with the experimental results. We also find the self-consistent ionization potentials to be often better than the non-self-consistent G0W0 values. We conclude that GW calculations should be done self-consistently in order to obtain physically meaningful and unambiguous energy differences.

71.15.-m - Methods of electronic structure calculations.
31.15.Lc - Quasiparticle methods.

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