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Assessing Recent Time-Dependent Double-Hybrid Density Functionals on Doublet-Doublet Excitations.

Joshua Van Dijk1, Marcos Casanova-Páez1,2, Lars Goerigk1

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ACS Physical Chemistry Au
|March 1, 2023
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Summary
This summary is machine-generated.

This study evaluates time-dependent double-hybrid density functionals (DHDFs) for calculating doublet-doublet excitation energies in radicals. Spin-scaled, range-separated DHDFs with the Tamm-Dancoff approximation (TDA) show promising results for accurate excitation energy calculations.

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Area of Science:

  • Computational Chemistry
  • Quantum Chemistry
  • Theoretical Chemistry

Background:

  • Accurate calculation of excitation energies is crucial for understanding radical chemistry.
  • Time-dependent double-hybrid density functionals (DHDFs) are advanced methods for electronic structure calculations.
  • Previous studies have focused on singlet excitations, leaving doublet excitations less explored.

Purpose of the Study:

  • To comprehensively investigate time-dependent double-hybrid density functionals (DHDFs) for doublet-doublet excitation energies.
  • To analyze the impact of approximations like TDA, range separation, and SCS/SOS on accuracy.
  • To identify the most reliable functionals for open-shell systems.

Main Methods:

  • Evaluation of 29 hybrid and DHDFs.
  • Assessment of 45 doublet-doublet excitations in 23 radicals.
  • Analysis of Tamm-Dancoff approximation (TDA), range separation, and spin-component/opposite scaling (SCS/SOS) effects.

Main Results:

  • Semiempirical DHDFs generally outperform nonempirical ones.
  • Spin-scaled, range-separated DHDFs combined with TDA are highly effective.
  • Specific functionals like TDA-SOS-ωB88PP86 and TDA-SOS-ωPBEPP86 are identified as robust.

Conclusions:

  • Certain spin-scaled, range-separated DHDFs with TDA offer a good balance of accuracy and computational cost.
  • These methods are recommended for general excitation energy calculations, especially for challenging open-shell systems.
  • Further improvements are needed to consistently surpass the chemical accuracy threshold for difficult cases.