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Transition Moments for STEOM-CCSD with Core Triples.
Megan Simons1, Devin A Matthews1
1Department of Chemistry, Southern Methodist University, Dallas, Texas 75275, United States.
Journal of Chemical Theory and Computation
|July 12, 2023
Summary
Similarity-transformed equation-of-motion coupled-cluster theory (STEOM-CC) provides accurate transition moments for core-excited states. This study extends STEOM-CC to include triple excitations, improving calculations for various electronic transitions.
Area of Science:
- Quantum Chemistry
- Computational Spectroscopy
- Theoretical Chemistry
Background:
- Equation-of-motion coupled-cluster theory (EOM-CC) is a standard method for calculating excited states.
- Similarity-transformed equation-of-motion coupled-cluster theory (STEOM-CC) offers an alternative approach using a second similarity transformation.
- Transition moments are crucial for understanding light-matter interactions in processes like absorption and emission.
Purpose of the Study:
- To derive and compute transition moments for core-excited states using the extended CVS-STEOM-CCSD+cT method.
- To investigate the inclusion of core triple excitations in transition moment calculations.
- To compare the performance of CVS-STEOM-CCSD+cT with existing methods like CVS-STEOMEE-CCSD and CVS-EOMEE-CCSD.
Main Methods:
- Development of transition moment calculations for core-excited states within the CVS-STEOM-CCSD+cT framework.
- Inclusion of core triple excitations and core-valence separation.
- Application and comparison of the method to a benchmark set of small molecules.
Main Results:
- Successfully derived transition moments for core-excited states, including ground-to-core-excited and valence-to-core-excited transitions.
- Demonstrated the capability of CVS-STEOM-CCSD+cT to accurately compute transition moments with core triple excitations.
- Showcased improvements in computed transition moments compared to standard CVS-STEOMEE-CCSD and CVS-EOMEE-CCSD.
Conclusions:
- The CVS-STEOM-CCSD+cT method provides a robust and accurate approach for calculating transition moments of core-excited states.
- The inclusion of core triple excitations significantly enhances the accuracy of transition moment predictions.
- This advancement offers improved theoretical tools for studying core-level spectroscopy and related phenomena.
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