{
  "abstract": "The low-energy nuclear isomeric transition of $^{229}$Th is a promising frequency reference for a solid-state nuclear optical clock. Wide-band-gap fluoride crystals such as CaF$_2$ offer transparent hosts for embedding Th nuclei at high density. Substitution of Th$^{4+}$ for Ca$^{2+}$ requires charge compensation, linking the local defect structure to nuclear quadrupole splitting. We use first-principles calculations to examine neutral Th dimers compensated by four interstitial F ions ($\\mathrm{F}_{i}^{-}$). Screening different compensation geometries by their relative formation energies identifies a family of low-energy configurations with closely similar local structures. These configurations share large electric field gradients and small asymmetry parameters, consistent with the experimental high-EFG site 3. Their calculated quadrupole splittings are further compared with the measured C13 spectra. Together, the energetic and spectroscopic results support $\\mathrm{F}_{i}^{-}$-compensated Th dimers as candidate microscopic structures for site 3 in Th:CaF$_2$.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.39288",
  "author_total": 10,
  "authors": [
    {
      "name": "Yuxiang Li"
    },
    {
      "name": "Lin Li"
    },
    {
      "name": "Qiaorui Gong"
    },
    {
      "name": "Shanming Li"
    },
    {
      "name": "Chengchun Zhao"
    },
    {
      "name": "Lu Deng"
    },
    {
      "name": "Peixiong Zhang"
    },
    {
      "name": "Yin Hang"
    },
    {
      "name": "Longsheng Ma"
    },
    {
      "name": "Shining Zhu"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/cdkgktr3dmvm5.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.39288",
  "fulltext_url": null,
  "id": "cdkgktr3dmvm5",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.39288",
  "language": null,
  "licence": "CC-BY-NC-ND-4.0",
  "licence_label": "CC BY-NC-ND 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cond-mat.mtrl-sci"
    ],
    [
      "arxiv",
      "physics.optics"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2610.39288",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-29",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/cdkgktr3dmvm5.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:36:23Z",
      "native_id": "2610.39288",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.39288"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mtrl-sci",
      "subfield": "condensed-matter"
    },
    {
      "field": "physics",
      "origin": "arxiv:physics.optics",
      "subfield": "optics-photonics"
    }
  ],
  "title": "Th$^{4+}$ ion cluster structures and electric field gradients in $^{229}$Th:CaF$_2$",
  "title_text": "Th^4+ ion cluster structures and electric field gradients in ^229Th:CaF_2",
  "type": "preprint",
  "updated_at": "2026-11-01T12:20:45Z",
  "url": "https://research.draconitic.com/paper/cdkgktr3dmvm5",
  "venue": "arXiv",
  "versions": []
}