On the Functional Dependence of Transition-Potential Coupled Cluster
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866917957268930560 |
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| author | Delgado, Alexis A. A. Matthews, Devin A. |
| author_facet | Delgado, Alexis A. A. Matthews, Devin A. |
| contents | Orbital relaxation of the core region is a primary source of error in the computation of core ionization and core excitation energies. Recently, Transition-Potential Coupled Cluster (TP-CC) methods have been used to explicitly treat orbital relaxation using non-variational molecular orbitals determined by reoccupation of orbitals optimized for a fractional core occupation. The amount of fractional occupation is governed by parameter $λ$, and recommended values for accurate TP-CCSD and XTP-CCSD computations of carbon, nitrogen, oxygen, and fluorine 1s K-edges were previously determined. Herein, we explore the performance of a several density functionals for generating the fractionally occupied orbitals used in TP-CCSD. These functionals include HF, BP86, BH&HLYP, B3LYP, M06-2X, and $ω$B97m-V. The fractionally occupied orbitals computed across the various functionals were subsequently employed as the initial orbitals for our TP-CCSD calculations of organic K-edge x-ray absorption and photoelectron spectra. Regardless of the functional used to generate the fractionally occupied orbitals, the TP-CCSD calculations yield accurate and comparable core ionization energies, core excitation energies, and oscillator strengths. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_11558 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | On the Functional Dependence of Transition-Potential Coupled Cluster Delgado, Alexis A. A. Matthews, Devin A. Chemical Physics Orbital relaxation of the core region is a primary source of error in the computation of core ionization and core excitation energies. Recently, Transition-Potential Coupled Cluster (TP-CC) methods have been used to explicitly treat orbital relaxation using non-variational molecular orbitals determined by reoccupation of orbitals optimized for a fractional core occupation. The amount of fractional occupation is governed by parameter $λ$, and recommended values for accurate TP-CCSD and XTP-CCSD computations of carbon, nitrogen, oxygen, and fluorine 1s K-edges were previously determined. Herein, we explore the performance of a several density functionals for generating the fractionally occupied orbitals used in TP-CCSD. These functionals include HF, BP86, BH&HLYP, B3LYP, M06-2X, and $ω$B97m-V. The fractionally occupied orbitals computed across the various functionals were subsequently employed as the initial orbitals for our TP-CCSD calculations of organic K-edge x-ray absorption and photoelectron spectra. Regardless of the functional used to generate the fractionally occupied orbitals, the TP-CCSD calculations yield accurate and comparable core ionization energies, core excitation energies, and oscillator strengths. |
| title | On the Functional Dependence of Transition-Potential Coupled Cluster |
| topic | Chemical Physics |
| url | https://arxiv.org/abs/2503.11558 |