Spin Symmetry in Thermally-Assisted-Occupation Density Functional Theory
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arXiv
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| Format: | Preprint |
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2024
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| _version_ | 1866911915268112384 |
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| author | Wang, Yu-Yang Chai, Jeng-Da |
| author_facet | Wang, Yu-Yang Chai, Jeng-Da |
| contents | For electronic systems with multi-reference (MR) character, Kohn-Sham density functional theory (KS-DFT) with the conventional exchange-correlation (xc) energy functionals can lead to incorrect spin densities and related properties. For example, for H2 dissociation, the spin-restricted and spin-unrestricted solutions obtained with the same xc energy functional in KS-DFT can be distinctly different, yielding the unphysical spin-symmetry breaking effects in the spin-unrestricted solutions. Recently, thermally-assisted-occupation density functional theory (TAO-DFT) has been shown to resolve the aforementioned spin-symmetry breaking, when the fictitious temperature is properly chosen. In this work, a response theory based on TAO-DFT is developed to demonstrate that TAO-DFT with a sufficiently large fictitious temperature can always resolve the unphysical spin-symmetry breaking in MR systems. To further support this, TAO-DFT calculations with various fictitious temperatures are performed for the dissociation of H2, N2, He2, and Ne2 as well as the twisted ethylene. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2405_09187 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Spin Symmetry in Thermally-Assisted-Occupation Density Functional Theory Wang, Yu-Yang Chai, Jeng-Da Chemical Physics Materials Science Computational Physics Quantum Physics For electronic systems with multi-reference (MR) character, Kohn-Sham density functional theory (KS-DFT) with the conventional exchange-correlation (xc) energy functionals can lead to incorrect spin densities and related properties. For example, for H2 dissociation, the spin-restricted and spin-unrestricted solutions obtained with the same xc energy functional in KS-DFT can be distinctly different, yielding the unphysical spin-symmetry breaking effects in the spin-unrestricted solutions. Recently, thermally-assisted-occupation density functional theory (TAO-DFT) has been shown to resolve the aforementioned spin-symmetry breaking, when the fictitious temperature is properly chosen. In this work, a response theory based on TAO-DFT is developed to demonstrate that TAO-DFT with a sufficiently large fictitious temperature can always resolve the unphysical spin-symmetry breaking in MR systems. To further support this, TAO-DFT calculations with various fictitious temperatures are performed for the dissociation of H2, N2, He2, and Ne2 as well as the twisted ethylene. |
| title | Spin Symmetry in Thermally-Assisted-Occupation Density Functional Theory |
| topic | Chemical Physics Materials Science Computational Physics Quantum Physics |
| url | https://arxiv.org/abs/2405.09187 |