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Media type:
E-Article
Title:
Accuracy of the distinguishable cluster approximation for triple excitations for open-shell molecules and excited states
Contributor:
Schraivogel, Thomas;
Kats, Daniel
imprint:
AIP Publishing, 2021
Published in:The Journal of Chemical Physics
Language:
English
DOI:
10.1063/5.0059181
ISSN:
0021-9606;
1089-7690
Origination:
Footnote:
Description:
<jats:p>The distinguishable cluster approximation for triple excitations has been applied to calculate thermochemical properties and excited states involving closed-shell and open-shell species, such as small molecules, 3d transition metal atoms, ozone, and an iron–porphyrin model. Excitation energies have been computed using the ΔCC approach by directly optimizing the excited states. A fixed-reference technique has been introduced to target selected spin-states for open-shell molecular systems. The distinguishable cluster approximation consistently improves coupled cluster with singles doubles and triples results for absolute and relative energies. For excited states dominated by a single configuration state function, the fixed-reference approach combined with high-level coupled-cluster methods has a comparable accuracy to the corresponding equation-of-motion coupled-cluster methods with a negligible amount of spin contamination.</jats:p>