A Mountaineering Strategy to Excited States: Accurate Vertical Transition Energies and Benchmarks for Substituted Benzenes
arxiv(2024)
摘要
To expand the existing QUEST database of accurate vertical transition
energies [\href{https://doi.org/10.1002/wcms.1517}{V\'eril et al.~\textit{WIREs
Comput.~Mol.~Sci.} \textbf{2021}, \textit{11}, e1517}], we have modeled more
than 100 electronic excited states of different natures (local,
charge-transfer, Rydberg, singlet, and triplet) in a dozen of mono- and
di-substituted benzenes, including aniline, benzonitrile, chlorobenzene,
fluorobenzene, nitrobenzene, among others. To establish theoretical best
estimates for these vertical excitation energies, we have employed advanced
coupled-cluster methods including iterative triples (CC3 and CCSDT) and, when
technically possible, iterative quadruples (CC4). These high-level
computational approaches provide a robust foundation for benchmarking a series
of popular wave function methods. The evaluated methods all include
contributions from double excitations (ADC(2), CC2, CCSD, CIS(D), EOM-MP2,
STEOM-CCSD), along with schemes that also incorporate perturbative or iterative
triples (ADC(3), CCSDR(3), CCSD(T)(a)$^\star$, and CCSDT-3). This systematic
exploration not only broadens the scope of the QUEST database but also
facilitates a rigorous assessment of different theoretical approaches in the
framework of a homologous chemical series, offering valuable insights into the
accuracy and reliability of these methods in such cases. We found that both
ADC(2.5) and CCSDT-3 can provide consistent estimates, whereas among less
expensive methods SCS-CC2 is likely the most effective approach. Importantly,
we show that some lower order methods may offer reasonable trends in the
homologous series while providing quite large average errors, and \emph{vice
versa}. Consequently, benchmarking the accuracy of a model based solely on
absolute transition energies may not be meaningful for applications involving a
series of similar compounds.
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