{
  "abstract": "Bulk hexagonal diamond has been synthesized by independent routes, but its structure remains contested: the two recent refinements disagree even on the sign of the difference between its two inequivalent bond lengths, 238~mÅ apart, and both depart from an earlier 2003 refinement. Here we test the competing structures with first-principles lattice dynamics. Relaxed hexagonal diamond has an interlayer bond \\emph{longer} than the intralayer bonds by 24~mÅ in both functionals, an effect of its eclipsed conformation that scales with polytype hexagonality. The bright zone-center $A_{1g}$ mode gauges the interlayer bond at $\\approx\\!-2{,}100$~\\icm~Å$^{-1}$, and neither refined coordinate reproduces the full pattern of measured modes. The only structure matching the twinned sample's three bands requires tens-of-gigapascals confining stress and lattice constants excluded by its own diffraction. Raman spectroscopy and diffraction jointly select a small positive bond asymmetry: inverting the spectrum of the phase-pure sample gives $\\OB-\\OA=24\\pm3$~mÅ (95\\% interval), and two determinations on separate samples give $+33\\pm8$ and $+60\\pm45$~mÅ. The 1{,}529~\\icm{} feature cannot be assigned to homogeneous ideal 2H diamond, and the local HRTEM observation remains an open puzzle.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2608.00138",
  "author_total": 1,
  "authors": [
    {
      "name": "Li Zhu"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/3f4q25q4pzp09.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2608.00138",
  "fulltext_url": null,
  "id": "3f4q25q4pzp09",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2608.00138",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cond-mat.mtrl-sci"
    ],
    [
      "arxiv",
      "physics.chem-ph"
    ],
    [
      "openalex",
      "2505|Diamond and Carbon-based Materials Research"
    ]
  ],
  "openalex": "W7172433675",
  "pdf_url": "https://arxiv.org/pdf/2608.00138",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-16",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/3f4q25q4pzp09.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:22:01Z",
      "native_id": "2608.00138",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2608.00138"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "arxiv:physics.chem-ph",
      "subfield": "physical"
    },
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.mtrl-sci",
      "subfield": "condensed-matter"
    }
  ],
  "title": "Vibrational spectroscopy identifies the bond asymmetry of hexagonal diamond",
  "title_text": "Vibrational spectroscopy identifies the bond asymmetry of hexagonal diamond",
  "type": "preprint",
  "updated_at": "2026-10-30T12:22:01Z",
  "url": "https://research.draconitic.com/paper/3f4q25q4pzp09",
  "venue": "arXiv",
  "versions": []
}