{
  "abstract": "Exploring the potential energy surfaces of molecules in optical cavities requires analytical derivatives. We present analytical nuclear gradients and nonadiabatic derivative couplings for state-averaged quantum-electrodynamics complete-active-space self-consistent field theory (SA-QED-CASSCF) forthe coherent-state Pauli–Fierz Hamiltonian, including the coupledperturbed response of the QED-Hartree–Fock reference and the photon contribution to the coupling that arises because the coherent-state displacement depends on the geometry. The derivatives agree with finite differences to within 10−6 atomic units (5×10−6 for the state of smallest weight in an unequal average) for equal, unequal and zero-weight state averaging, and with independent codes without the cavity. With them we locate a polariton-induced conical intersection in LiH, where the cavity makes the molecular orientation a second coordinate and a reflection combined with photon parity makes the crossing symmetry-allowed. In ethylene, the S0/S1 conical intersection persists under coupling and keeps its twisted–pyramidalized geometry, and it becomes more accessible from the Franck–Condon point, because the dipole self-energy raises the diffuse π → 3s state more than the crossing pair. Capturing the partial return of this penalty through the bilinear coupling requires the polarization-axis partner orbital in the active space, a rule for polaritonic CASSCF in general.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": null,
  "author_total": 2,
  "authors": [
    {
      "name": "Nam Vu"
    },
    {
      "name": "Jonathan J. Foley",
      "orcid": "0000-0001-8814-4444"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/6bbv3nc2fk9k0.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15009951/v1",
  "fulltext_url": null,
  "id": "6bbv3nc2fk9k0",
  "issns": [],
  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009951/v1",
  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "3107|Strong Light-Matter Interactions"
    ]
  ],
  "openalex": "W7220725320",
  "pdf_url": "https://chemrxiv.org/doi/pdf/10.26434/chemrxiv.15009951/v1",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-05",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/6bbv3nc2fk9k0.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:22Z",
      "native_id": "10.26434/chemrxiv.15009951",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009951/v1"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "openalex:3107|Strong Light-Matter Interactions",
      "subfield": "amo"
    }
  ],
  "title": "Analytic Nuclear Gradients and Derivative Couplings for SA-QED-CASSCF",
  "title_text": "Analytic Nuclear Gradients and Derivative Couplings for SA-QED-CASSCF",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:22Z",
  "url": "https://research.draconitic.com/paper/6bbv3nc2fk9k0",
  "venue": "ChemRxiv",
  "versions": []
}