{
  "abstract": "Nonadiabatic molecular dynamics is essential for simulating photoinduced processes, but its application to large molecular systems is often limited by the cost of repeatedly evaluating excited-state energies, forces, and nonadiabatic couplings. Here, we present a GPU-accelerated implementation of trajectory surface hopping within PYSEQM (https://github.com/lanl/PYSEQM/), a PyTorch-based semiempirical quantum chemistry framework. The module combines semiempirical model Hamiltonians with configuration-interaction singles excited states and introduces the nonadiabatic coupling vectors and time-derivative couplings required for surface-hopping dynamics. The implementation further includes treatments of trivial crossings and electronic decoherence, providing a complete framework for propagating coupled electronic and nuclear dynamics. To improve GPU utilization, independent trajectories are propagated concurrently in batches. Benchmark calculations show that this strategy substantially increases aggregate simulation throughput as the batch size is increased for small molecules. We demonstrate the applicability of the method to large molecular systems by simulating the excited-state population dynamics of methyl-and tert-butyl substituted molecular nanostar dendrimers, which contain dense manifolds of electronically excited states. These calculations show that semiempirical surface-hopping dynamics can be extended to molecular systems that remain challenging for conventional ab-initio approaches. In addition, the differentiable PyTorch formulation provides a data-science route for optimizing semiempirical Hamiltonian parameters against reference excited-state properties and, ultimately, dynamical observables. PYSEQM therefore provides a platform for high-throughput nonadiabatic molecular dynamics and for the development of data-driven semiempirical models for photophysics and photochemistry.",
  "abstract_shown": true,
  "affiliations": [
    "Theoretical Division",
    "Los Alamos National Laboratory",
    "Departamento de Ciencia y Tecnologia",
    "Universidad Nacional de Quilmes/CONICET",
    "Department of Chemistry",
    "University of Florida",
    "Quantum Theory Project"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 6,
  "authors": [
    {
      "affs": [
        0,
        1
      ],
      "name": "Vishikh Athavale",
      "orcid": "0000-0002-0571-2336"
    },
    {
      "affs": [
        2,
        3
      ],
      "name": "Sebastian Fernandez-Alberti"
    },
    {
      "affs": [
        4,
        5,
        6
      ],
      "name": "Adrian E. Roitberg"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Maksim Kulichenko"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Anders M. N. Niklasson"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "Sergei Tretiak"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/b2ftm10wafjw6.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15008290/v1",
  "fulltext_url": null,
  "id": "b2ftm10wafjw6",
  "issns": [],
  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008290/v1",
  "language": null,
  "licence": "CC-BY-NC-ND",
  "licence_label": "CC BY-NC-ND",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "3107|Advanced Chemical Physics Studies"
    ]
  ],
  "openalex": "W7208751629",
  "pdf_url": "https://chemrxiv.org/doi/pdf/10.26434/chemrxiv.15008290/v1",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-04",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/b2ftm10wafjw6.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:17Z",
      "native_id": "10.26434/chemrxiv.15008290",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008290/v1"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "openalex:3107|Advanced Chemical Physics Studies",
      "subfield": "amo"
    }
  ],
  "title": "GPU-Accelerated Large-Scale Nonadiabatic Excited State Molecular Dynamics",
  "title_text": "GPU-Accelerated Large-Scale Nonadiabatic Excited State Molecular Dynamics",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:17Z",
  "url": "https://research.draconitic.com/paper/b2ftm10wafjw6",
  "venue": "ChemRxiv",
  "versions": []
}