The difficulty of widely used density functionals in describing the dissociation behavior of some homonuclear and heteronuclear diatomic radicals is analyzed. It is shown that the self-interaction error of these functionals accounts for the problem—it is much larger for a system with a noninteger number of electrons than a system with an integer number of electrons. We find the condition for the erroneous dissociation behavior described by approximate density functionals: when the ionization energy of one dissociation partner differs from the electron affinity of the other partner by a small amount, the self-interaction error will lead to wrong dissociation limit. Systems with a noninteger number of electrons and hence the large amount of self-interaction error in approximate density functionals arise also in the transition states of some chemical reactions and in some charge-transfer complexes. In the course of analysis, we derive a scaling relation necessary for an exchange-correlation functional to be self-interaction free.
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15 August 1998
Research Article|
August 15 1998
A challenge for density functionals: Self-interaction error increases for systems with a noninteger number of electrons
J. Chem. Phys. 109, 2604–2608 (1998)
Article history
Received:
March 02 1998
Accepted:
May 12 1998
Citation
Yingkai ZhangWeitao Yang; A challenge for density functionals: Self-interaction error increases for systems with a noninteger number of electrons. J. Chem. Phys. 15 August 1998; 109 (7): 2604–2608. https://doi.org/10.1063/1.476859
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