2021/05/26 by Pierre-François Loos, Pierre‐François Loos, Devin A. Matthews +2 · 31 citations
Chemistry · Physics and Astronomy · #Advanced Chemical Physics Studies #Atomic physics #Cluster (spacecraft) #Computer science #Coupled cluster #Excitation #Excited state #Molecule #Photochemistry and Electron Transfer Studies #Physics #Quantum mechanics #Set (abstract data type) #Spectroscopy and Quantum Chemical Studies #cond-mat.mtrl-sci #cond-mat.str-el #physics.chem-ph #physics.comp-ph
paper · pdf · doi:10.1063/5.0055994
published in The Journal of Chemical Physics 154(22), 221103 (American Institute of Physics) · 6 pages, 2 figures
arxiv created 2021/05/26 · openalex publication_date 2021/06/11 · arxiv updated 2021/06/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We report the first investigation of the performance of EOM-CC4—an approximate equation-of-motion coupled-cluster model, which includes iterative quadruple excitations—for vertical excitation energies in molecular systems. By considering a set of 28 excited states in 10 small molecules for which we have computed CC with singles, doubles, triples, quadruples, and pentuples and full configuration interaction reference energies, we show that, in the case of excited states with a dominant contribution from the single excitations, CC4 yields excitation energies with sub-kJ mol−1 accuracy (i.e., error below 0.01 eV), in very close agreement with its more expensive CC with singles, doubles, triples, and quadruples parent. Therefore, if one aims at high accuracy, CC4 stands as a highly competitive approximate method to model molecular excited states, with a significant improvement over both CC3 and CC with singles, doubles, and triples. Our results also evidence that, although the same qualitative conclusions hold, one cannot reach the same level of accuracy for transitions with a dominant contribution from the double excitations.