Next Article in Journal / Special Issue
First Principles Molecular Dynamics Study of Catalysis for Polyolefins: the Ziegler-Natta Heterogeneous System.
Previous Article in Journal / Special Issue
Chemical Reactivity Dynamics and Quantum Chaos in Highly Excited Hydrogen Atoms in an External Field: A Quantum Potential Approach
Int. J. Mol. Sci. 2002, 3(4), 360-394; doi:10.3390/i3040360
Article

Can Unrestricted Density-Functional Theory Describe Open Shell Singlet Biradicals?

, ,  and *
Received: 29 August 2001; Accepted: 17 December 2001 / Published: 25 April 2002
(This article belongs to the Special Issue Application of Density Functional Theory)
Download PDF [242 KB, uploaded 19 June 2014]
Abstract: Unrestricted density functional theory (UDFT) can be used for the description of open-shell singlet (OSS) biradicals provided a number of precautions are considered. Biradicals that require a two-determinantal wave function (e.g. OSS state of carbenes) cannot be described by UDFT for principal reasons. However, if the overlap between the open-shell orbitals is small (the single electrons are located at different atomic centers) errors become small and, then, the principal failure of UDFT in these cases is not apparent and may even be disguised by the fact that UDFT has the advantage of describing spin polarization better than any restricted open shell DFT method. In the case of OSS biradicals with two- or multiconfigurational character (but a onedeterminantal form of the leading configuration), reasonable results can be obtained by broken-symmetry (BS)-UDFT, however in each case this has to be checked. In no case is it reasonable to lower the symmetry of a molecule to get a suitable UDFT description. Hybrid functionals such as B3LYP perform better than pure DFT functionals in BS-UDFT calculations because the former reduce the self-interaction error of DFT exchange functionals, which mimics unspecified static electron correlation effects, so that the inclusion of specific static electron correlation effects via the form of the wavefunction becomes more effective.
Keywords: Unrestricted Density Functional Theory (UDFT); non-dynamic electron correlation; biradicals; spin contamination Unrestricted Density Functional Theory (UDFT); non-dynamic electron correlation; biradicals; spin contamination
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Export to BibTeX |
EndNote


MDPI and ACS Style

Gräfenstein, J.; Kraka, E.; Filatov, M.; Cremer, D. Can Unrestricted Density-Functional Theory Describe Open Shell Singlet Biradicals? Int. J. Mol. Sci. 2002, 3, 360-394.

AMA Style

Gräfenstein J, Kraka E, Filatov M, Cremer D. Can Unrestricted Density-Functional Theory Describe Open Shell Singlet Biradicals? International Journal of Molecular Sciences. 2002; 3(4):360-394.

Chicago/Turabian Style

Gräfenstein, Jürgen; Kraka, Elfi; Filatov, Michael; Cremer, Dieter. 2002. "Can Unrestricted Density-Functional Theory Describe Open Shell Singlet Biradicals?" Int. J. Mol. Sci. 3, no. 4: 360-394.


Int. J. Mol. Sci. EISSN 1422-0067 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert