| Autor: |
David, Grégoire, Trinquier, Georges, Malrieu, Jean-Paul |
| Předmět: |
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| Zdroj: |
Journal of Chemical Physics; 11/21/2020, Vol. 153 Issue 19, p1-10, 10p |
| Abstrakt: |
Broken-symmetry calculations of diradicals exploit the mean-field energies of determinants that are not eigenfunctions of the Ŝ 2 operator, the mean value of which is close to 1 for the ms = 0 solution. This spin contamination must be corrected. Two different contributions affect ⟨ Ŝ 2 ⟩ , namely, the mixing between neutral and ionic valence bond components, the so-called kinetic exchange, which decreases ⟨ Ŝ 2 ⟩ , and the spin polarization of the supposedly closed shell orbitals, which increases ⟨ Ŝ 2 ⟩. The popular Yamaguchi formula is valid for the first effect but irrelevant for the second one. From a few constrained broken-symmetry calculations, one may treat separately the two contributions and apply their specific spin decontamination correction. This work proposes a consistent spin-decontaminated procedure for the evaluation of singlet–triplet gaps in diradicals. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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