Long-range and short-range Coulomb correlation effects as simulated by Hartree–Fock,local density approximation,and generalized gradient approximation exchange functionals |
| |
Authors: | Victor Polo Jürgen Gräfenstein Elfi Kraka Dieter Cremer |
| |
Institution: | 1.Department of Theoretical Chemistry, G?teborg University, Reutersgatan 2, 413 20 G?teborg, Sweden,SE |
| |
Abstract: | Exchange functionals used in density functional theory (DFT) are generally considered to simulate long-range electron correlation
effects. It is shown that these effects can be traced back to the self-interaction error (SIE) of approximate exchange functionals.
An analysis of the SIE with the help of the exchange hole reveals that both short-range (dynamic) and long-range (nondynamic)
electron correlation effects are simulated by DFT exchange where the local density approximation (LDA) accounts for stronger
effects than the generalized gradient expansion (GGA). This is a result of the fact that the GGA exchange hole describes the
exact exchange hole close to the reference electron more accurately than the LDA hole does. The LDA hole is more diffuse,
thus leading to an underestimation of exchange and stronger SIE effects, where the magnitude of the SIE energy is primarily
due to the contribution of the core orbitals. The GGA exchange hole is more compact, which leads to an exaggeration of exchange
in the bond and the nonbonding region and negative SIE contributions. Partitioning of the SIE into intra-/interelectronic
and individual orbital contributions makes it possible to test the performance of a given exchange functional in different
regions of the molecule. It is shown that Hartree–Fock exchange always covers some long-range effects via interelectronic
exchange while self-interaction-corrected DFT is lacking these effects.
Received: 25 May 2002 / Accepted: 7 October 2002 / Published online: 21 January 2003
Correspondence to: E. Kraka e-mail: kraka@theoc.gn.se
Acknowledgements. This work was supported financially by the Swedish Natural Science Research Council (NFR). Calculations were done on the
supercomputers of Nationellt Superdatorcentrum (NSC), Link?ping, Sweden. The authors thank the NSC for a generous allotment
of computer time. |
| |
Keywords: | : Self-interaction error – Dynamic electron correlation – GGA exchange hole – LDA exchange hole |
本文献已被 SpringerLink 等数据库收录! |
|