Vibrationally resolved coupled-cluster x-ray absorption spectra from vibrational configuration interaction anharmonic
Torsha Moitra1, Diana Madsen2, Ove Christiansen2
1DTU Chemistry-Department of Chemistry, Technical University of Denmark, Kemitorvet Bldg. 207, DK-2800 Kongens Lyngby, Denmark.
The Journal of Chemical Physics
|December 23, 2020
Summary
This study computes vibrationally resolved K-edge X-ray absorption spectra for small molecules using advanced computational methods. The results provide detailed insights into molecular electronic structures and vibrational dynamics.
Area of Science:
- Quantum Chemistry
- Spectroscopy
- Computational Molecular Science
Background:
- Near-edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy provides insights into electronic structure.
- Accurate computation of vibrational effects is crucial for interpreting NEXAFS spectra.
Purpose of the Study:
- To compute vibrationally resolved K-edge X-ray absorption spectra for small molecules.
- To develop and apply advanced computational methods for spectral prediction.
- To investigate the role of anharmonicity and coupling terms in molecular potentials.
Main Methods:
- Anharmonic vibrational configuration interaction calculations
- Franck-Condon factor computations
- Core-valence separated CC2, CCSD, CCSDR(3), and CC3 levels of theory
- Adaptive density-guided approach for selecting energy calculation points
- Inclusion of pair-mode coupling terms for polyatomic molecules
Main Results:
- Successfully computed vibrationally resolved K-edge X-ray absorption spectra.
- Potential energy surfaces for ground and core-excited states were accurately determined.
- Demonstrated the feasibility of including pair-mode coupling for improved potential descriptions.
Conclusions:
- The developed computational approach enables accurate prediction of NEXAFS spectra.
- Anharmonic effects and coupling terms are important for precise spectral interpretation.
- This work advances the computational study of molecular spectroscopy.
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