TD$Δ$SCF: Time-Dependent Density Functional Theory with a Non-Aufbau Reference for near-degenerate states
Fuente:
arXiv
Enregistré dans:
| Auteurs principaux: | , , |
|---|---|
| Format: | Preprint |
| Publié: |
2026
|
| Sujets: | |
| Accès en ligne: | |
| Tags: |
Ajouter un tag
Pas de tags, Soyez le premier à ajouter un tag!
|
| _version_ | 1866917476357373952 |
|---|---|
| author | Shibasaki, Shuto Mohri, Fumiya Tsuchimochi, Takashi |
| author_facet | Shibasaki, Shuto Mohri, Fumiya Tsuchimochi, Takashi |
| contents | Near-degenerate electronic structures remain a major challenge for conventional single-reference density functional theory (DFT). To address this problem, we propose time-dependent $Δ$SCF (TD$Δ$SCF), a novel linear-response scheme in which a non-Aufbau $Δ$SCF determinant serves as the reference for a subsequent TDDFT calculation. In contrast to collinear spin-flip (SF)-TDDFT, this formulation preserves the usual Coulomb and exchange-correlation response contributions while describing the target states from an electronically excited reference. We examine the performance of TD$Δ$SCF for several prototypical problems involving near-degeneracy, including the torsional potential of ethylene, singlet--triplet gaps of representative diradicals, geometry optimizations of benzyne isomers, and bond-dissociation curves of hydrogen fluoride and F$_2$. Across these tests, TD$Δ$SCF shows markedly weaker functional dependence than SF-TDDFT and often yields a more balanced description of challenging singlet states. In particular, it provides smooth torsional potentials, improved singlet--triplet gaps, a consistent monocyclic structure for singlet $m$-benzyne, and a more satisfactory description of bond dissociation without the spurious low-lying states found in SF-TDDFT. At the same time, the method exhibits a systematic tendency to overestimate singlet energies and can lose accuracy when the underlying $Δ$SCF reference is not well suited to the final state. We also identify a numerical instability that can arise in non-Aufbau calculations and trace its origin to the exchange-correlation potential near uncompensated nodal regions. These results highlight both the promise and the practical limitations of TD$Δ$SCF as a low-cost method for singlet states with near-degenerate electronic structures. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_29948 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | TD$Δ$SCF: Time-Dependent Density Functional Theory with a Non-Aufbau Reference for near-degenerate states Shibasaki, Shuto Mohri, Fumiya Tsuchimochi, Takashi Chemical Physics Near-degenerate electronic structures remain a major challenge for conventional single-reference density functional theory (DFT). To address this problem, we propose time-dependent $Δ$SCF (TD$Δ$SCF), a novel linear-response scheme in which a non-Aufbau $Δ$SCF determinant serves as the reference for a subsequent TDDFT calculation. In contrast to collinear spin-flip (SF)-TDDFT, this formulation preserves the usual Coulomb and exchange-correlation response contributions while describing the target states from an electronically excited reference. We examine the performance of TD$Δ$SCF for several prototypical problems involving near-degeneracy, including the torsional potential of ethylene, singlet--triplet gaps of representative diradicals, geometry optimizations of benzyne isomers, and bond-dissociation curves of hydrogen fluoride and F$_2$. Across these tests, TD$Δ$SCF shows markedly weaker functional dependence than SF-TDDFT and often yields a more balanced description of challenging singlet states. In particular, it provides smooth torsional potentials, improved singlet--triplet gaps, a consistent monocyclic structure for singlet $m$-benzyne, and a more satisfactory description of bond dissociation without the spurious low-lying states found in SF-TDDFT. At the same time, the method exhibits a systematic tendency to overestimate singlet energies and can lose accuracy when the underlying $Δ$SCF reference is not well suited to the final state. We also identify a numerical instability that can arise in non-Aufbau calculations and trace its origin to the exchange-correlation potential near uncompensated nodal regions. These results highlight both the promise and the practical limitations of TD$Δ$SCF as a low-cost method for singlet states with near-degenerate electronic structures. |
| title | TD$Δ$SCF: Time-Dependent Density Functional Theory with a Non-Aufbau Reference for near-degenerate states |
| topic | Chemical Physics |
| url | https://arxiv.org/abs/2603.29948 |