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Updated: Jul 6, 2026
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Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
Published on: September 17, 2017
Benchmarks for electronically excited states: CASPT2, CC2, CCSD, and CC3
Marko Schreiber1, Mario R Silva-Junior, Stephan P A Sauer
1Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany.
The Journal of Chemical Physics
|April 10, 2008
Summary
This study benchmarks computational methods for calculating excited states of organic molecules. Coupled cluster methods (CC3) closely match CASPT2, providing reliable excitation energies for chromophores.
Area of Science:
- Computational chemistry
- Quantum chemistry
- Spectroscopy
Background:
- Accurate computation of molecular excited states is crucial for understanding photophysical processes.
- Existing methods require careful validation for diverse organic chromophores.
Purpose of the Study:
- To establish a benchmark set of medium-sized organic molecules for evaluating computational methods.
- To assess the accuracy of coupled cluster (CC2, CCSD, CC3) and CASPT2 methods for vertical excitation energies.
Main Methods:
- Assembled a benchmark set of 28 organic molecules representing key chromophore classes.
- Computed vertical excitation energies and one-electron properties using CASPT2, CC2, CCSD, and CC3.
- Performed calculations at identical geometries (MP2/6-31G*) with the TZVP basis set.
Main Results:
- CC3 and CASPT2 methods show excellent agreement for vertical excitation energies.
- CC2 generally outperforms CCSD in reproducing CC3 reference data, especially for singlet excited states.
- Statistical analysis of 223 excited states provides insights into method performance.
Conclusions:
- CC3 and CASPT2 are reliable methods for calculating excited states of organic chromophores.
- CC2 offers a good balance of accuracy and cost for singlet excited states.
- Proposed best estimates for 104 singlet and 63 triplet excited states based on computational results and literature review.
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