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Quantifying the error of the core-valence separation approximation
Michael F Herbst1, Thomas Fransson2
1CERMICS, École des Ponts ParisTech, 6-8 Avenue Blaise Pascal, 77455 Marne-la-Vallée, France; Inria Paris, 75589 Paris Cedex 12, France; and Sorbonne Universitée, Institut des Sciences du Calcul et des Données, ISCD, 75005 Paris, France.
The Journal of Chemical Physics
|August 11, 2020
Summary
We developed a post-processing method to eliminate errors in core-valence separation (CVS) calculations for X-ray absorption spectroscopy. This improves the accuracy of predicting core-excited states, crucial for understanding electronic structures.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Spectroscopy
Background:
- Core-valence separation (CVS) is essential for calculating core-excited states in X-ray absorption spectroscopy.
- The CVS scheme, while specific, introduces inherent errors in these calculations.
Purpose of the Study:
- To implement a post-processing step to remove errors from CVS excitations.
- To analyze the accuracy and error sources within the CVS scheme.
- To investigate the impact of basis set selection on CVS accuracy.
Main Methods:
- Algebraic-diagrammatic construction scheme for the polarization propagator.
- Post-processing of CVS excitations.
- Systematic analysis of error contributions and basis set effects.
Main Results:
- A novel post-processing method successfully eliminates CVS errors.
- CVS accuracy is limited by the balance of neglected core-valence and core-core excitations.
- Basis set choice, particularly tight polarizing functions, is critical for error balance.
- CVS error is system-independent and element-specific (±0.02 eV for K-edge).
Conclusions:
- The developed post-processing method enhances the reliability of CVS calculations.
- Understanding error sources provides insights into improving theoretical models for spectroscopy.
- Basis set optimization is key to achieving accurate core-excited state predictions.
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