التفاصيل البيبلوغرافية
| العنوان: |
Orbital dependent complications for close vs well-separated electrons in diradicals. |
| المؤلفون: |
Hooshmand, Zahra, Bravo Flores, Jose Gustavo, Pederson, Mark R. |
| المصدر: |
Journal of Chemical Physics; 12/21/2023, Vol. 159 Issue 23, p1-9, 9p |
| مصطلحات موضوعية: |
BIRADICALS, HARTREE-Fock approximation, ELECTRON configuration, ELECTRONS, ENERGY function |
| مستخلص: |
We investigate two limits in open-shell diradical systems: O3, in which the interesting orbitals are in close proximity to one another, and (C21H13)2, where there is a significant spatial separation between the two orbitals. In accord with earlier calculations, we find that standard density-functional approximations do not predict the open-shell character for the former case but uniformly predict the open-shell character for the latter case. We trace the qualitatively incorrect behavior in O3 predicted by these standard density functional approximations to self-interaction error and use the Fermi–Löwdin-orbital-self-interaction-corrected formalism to determine accurate triplet, closed-shell singlet, and open-shell broken-spin-symmetry electronic configurations. Analysis of the resulting many-electron overlap matrices allows us to unambiguously show that the broken-spin-symmetry configurations do not participate in the representation of the Ms = 0 triplet states and allows us to reliably extract the singlet–triplet splitting in O3 by analyzing the energy as a function of Fermi-orbital-descriptor permutations. The results of these analyses predict the percentage of open-shell character in O3, which agrees well with conventional wavefunction-based methods. While these techniques are expected to be required in cases near the Coulson–Fischer point, we find that they will be less necessary in diradical systems with well-separated electrons, such as (C21H13)2. Results based on energies from self-interaction-corrected generalized gradient, local density, and Hartree–Fock approximations and experimental results are in generally good agreement for O3. These results help form the basis for deriving extended Heisenberg-like Hamiltonians that are needed for descriptions of molecular magnets when there are competing low-energy electronic configurations. [ABSTRACT FROM AUTHOR] |
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| قاعدة البيانات: |
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