Transition-Potential Coupled Cluster II: Optimization of the Core Orbital Occupation Number
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arXiv
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| Format: | Preprint |
| Published: |
2022
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| _version_ | 1866913754975830016 |
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| author | Simons, Megan Matthews, Devin A. |
| author_facet | Simons, Megan Matthews, Devin A. |
| contents | The issue of orbital relaxation in computational core-hole spectroscopy, specifically x-ray absorption, has been a major problem for methods such as equation-of-motion coupled cluster with singles and doubles (EOM-CCSD). The transition-potential coupled cluster (TP-CC) method is utilized to address this problem by including an explicit treatment of orbital relaxation via the use of reference orbitals with a fractional core occupation number. The value of the fractional occupation parameter $λ$ was optimized for both TP-CCSD and XTP-CCSD methods in an element-specific manner due to the differences in atomic charge and energy scale. Additionally, TP-CCSD calculations using the optimized parameters were performed for the K-edge absorption spectra of gas-phase adenine and thymine. TP-CCSD reproduces the valence region well and requires smaller overall energy shifts in comparison to EOM-CCSD, while also improving on the relative position and intensities of several absorption peaks. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2204_05425 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | Transition-Potential Coupled Cluster II: Optimization of the Core Orbital Occupation Number Simons, Megan Matthews, Devin A. Chemical Physics The issue of orbital relaxation in computational core-hole spectroscopy, specifically x-ray absorption, has been a major problem for methods such as equation-of-motion coupled cluster with singles and doubles (EOM-CCSD). The transition-potential coupled cluster (TP-CC) method is utilized to address this problem by including an explicit treatment of orbital relaxation via the use of reference orbitals with a fractional core occupation number. The value of the fractional occupation parameter $λ$ was optimized for both TP-CCSD and XTP-CCSD methods in an element-specific manner due to the differences in atomic charge and energy scale. Additionally, TP-CCSD calculations using the optimized parameters were performed for the K-edge absorption spectra of gas-phase adenine and thymine. TP-CCSD reproduces the valence region well and requires smaller overall energy shifts in comparison to EOM-CCSD, while also improving on the relative position and intensities of several absorption peaks. |
| title | Transition-Potential Coupled Cluster II: Optimization of the Core Orbital Occupation Number |
| topic | Chemical Physics |
| url | https://arxiv.org/abs/2204.05425 |