{
  "abstract": "Nonadiabatic dynamics through a conical intersection requires both static and dynamic correlation and, at every geometry, an excited-state gradient and interstate nonadiabatic coupling (NACME). Analytic multireference derivatives at this level have been confined to datacenter-scale hardware. We report device-resident \\mbox{DMRG-QD-NEVPT2} with analytic gradients and NACMEs within the $8$\\,GB of a consumer GPU: a density-matrix-renormalization-group (DMRG) active-space reference supplies the static correlation, and quasi-degenerate SC-NEVPT2 dresses it through a multi-state effective Hamiltonian that remains valid \\emph{through} a conical intersection, where single-state perturbation theory develops a vanishing denominator and fails. Every gradient and NACME is one reverse-mode transpose of a single contraction graph: the DMRG sweep enters as a gauge-free differentiable node, and all two-electron work is AO-direct through Cholesky factors. The DMRG reference is exact within the active space ($\\sim\\!10^{-15}$\\,Ha). The corrected adiabats close smoothly to a real $S_0/S_1$ conical intersection with a non-vanishing, $1/ΔE$-divergent NACME---where linear-response TDDFT returns zero identically---and the dressing restores the differential dynamic correlation that ionic $ππ^*$ states require. DMRG-NEVPT2 and quasi-degenerate NEVPT2 are each established; what is new is the combined stack---multi-state and through a conical intersection, with analytic gradients and couplings---realized device-resident on commodity hardware.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.09990",
  "author_total": 1,
  "authors": [
    {
      "name": "Rubén Darío Guerrero"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/fa48vc6xdtnsx.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.09990",
  "fulltext_url": null,
  "id": "fa48vc6xdtnsx",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.09990",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cs.AR"
    ],
    [
      "arxiv",
      "physics.chem-ph"
    ],
    [
      "openalex",
      "3107|Advanced Chemical Physics Studies"
    ]
  ],
  "openalex": "W7212131190",
  "pdf_url": "https://arxiv.org/pdf/2609.09990",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-16",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/fa48vc6xdtnsx.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:22:01Z",
      "native_id": "2609.09990",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.09990"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "arxiv:physics.chem-ph",
      "subfield": "physical"
    }
  ],
  "title": "Analytic Gradients and Nonadiabatic Couplings for Device-Resident DMRG-QD-NEVPT2 Through Conical Intersections on a Consumer GPU",
  "title_text": "Analytic Gradients and Nonadiabatic Couplings for Device-Resident DMRG-QD-NEVPT2 Through Conical Intersections on a Consumer GPU",
  "type": "preprint",
  "updated_at": "2026-10-30T12:22:01Z",
  "url": "https://research.draconitic.com/paper/fa48vc6xdtnsx",
  "venue": "arXiv",
  "versions": []
}