{
  "abstract": "In a recent work [S. Yalouz and V. Robert, J. Chem. Theory Comput. 19, 1381 (2023)], we introduced the foundations of an orthogonally constrained complete active space self-consistent field (OC-CASSCF) framework that produces state-specific molecular orbitals for mutually orthogonal multiconfigurational electronic states. In the present study, we extend this approach by incorporating a Newton–Raphson orbital-optimization scheme, for which we derive the analytical expressions of the orbital gradient and Hessian. Furthermore, we outline a practical route toward the evaluation of analytical nuclear gradients, enabling geometry optimizations within the OC-CASSCF formalism. Benchmark calculations on the three lowest singlet states of LiH and H2O molecules demonstrate a systematic improvement as compared to conventional state-averaged CASSCF, even when using modestly sized active spaces.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": null,
  "author_total": 3,
  "authors": [
    {
      "name": "Loris Delafosse"
    },
    {
      "name": "Vincent Robert"
    },
    {
      "name": "Saad Yalouz"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/bhrpfhbe0maxa.bib",
  "cited_by": 0,
  "doi": "10.1063/5.0324860",
  "fulltext_url": null,
  "id": "bhrpfhbe0maxa",
  "issns": [
    "0021-9606",
    "1089-7690"
  ],
  "landing_url": "https://univoak.hal.science/hal-05754319v1",
  "language": "en",
  "licence": "CC-BY-NC-4.0",
  "licence_label": "CC BY-NC 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by-nc/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "hal",
      "0.chim"
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      "hal",
      "1.chim.theo"
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      "openalex",
      "3107|Advanced Chemical Physics Studies"
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  "openalex": "W7165527941",
  "pdf_url": "https://univoak.hal.science/hal-05754319/document",
  "pmcid": null,
  "pmid": null,
  "published": "2026-06-28",
  "publisher": "American Institute of Physics",
  "ris": "https://research.draconitic.com/paper/bhrpfhbe0maxa.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:36Z",
      "native_id": "hal-05754319",
      "source": "hal",
      "url": "https://univoak.hal.science/hal-05754319v1"
    }
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  "subjects": [
    {
      "field": "chemistry",
      "origin": "hal:1.chim.theo",
      "subfield": "theoretical"
    }
  ],
  "title": "Orthogonally constrained CASSCF framework: Newton–Raphson orbital optimization and nuclear gradients",
  "title_text": "Orthogonally constrained CASSCF framework: Newton–Raphson orbital optimization and nuclear gradients",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:17:36Z",
  "url": "https://research.draconitic.com/paper/bhrpfhbe0maxa",
  "venue": "The Journal of Chemical Physics",
  "versions": []
}