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PreprintCC BY 4.0arXiv

On the Spin Symmetry of Fractional-Occupation Mean-Field Approaches

  • Md Rafi Ul Azam
  • Rachel Campbell
  • Kay Carter-Fenk
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Abstract

We identify a spin-symmetry dilemma rooted in the representability problem of fractional-occupation densities, which break spin symmetry even for restricted orbital references. We propose a resolution that leverages complex polarization to restore pure-state N-representability and exact spin eigenstates while retaining improvements to the energy and density from occupation smearing. Our results have implications for widely-used smearing methods in solid-state simulation and for their use as a proxy for static correlation in molecules.

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Cite

BibTeXRIS
BibTeX
@misc{azam2026spin,
  title = {{On the Spin Symmetry of Fractional-Occupation Mean-Field Approaches}},
  author = {Md Rafi Ul Azam and Rachel Campbell and Kay Carter-Fenk},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.38224},
  eprint = {2610.38224},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.38224},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - On the Spin Symmetry of Fractional-Occupation Mean-Field Approaches
AU  - Md Rafi Ul Azam
AU  - Rachel Campbell
AU  - Kay Carter-Fenk
PY  - 2026
DA  - 2026/10/28
PB  - arXiv
DO  - 10.48550/arxiv.2610.38224
UR  - https://arxiv.org/abs/2610.38224
AB  - We identify a spin-symmetry dilemma rooted in the representability problem of fractional-occupation densities, which break spin symmetry even for restricted orbital references. We propose a resolution that leverages complex polarization to restore pure-state N-representability and exact spin eigenstates while retaining improvements to the energy and density from occupation smearing. Our results have implications for widely-used smearing methods in solid-state simulation and for their use as a proxy for static correlation in molecules.
ER  -