{
  "model": "Heisenberg",
  "lattice": "kagome-2x2",
  "n_sites": 12,
  "boundary": "P",
  "params": {},
  "instance_id": "Heisenberg/kagome-2x2_12_P",
  "rows": [
    {
      "energy": -21.779500864,
      "sigma": null,
      "energy_variance": null,
      "dof": 12,
      "einf": 0,
      "v_score": null,
      "method": "Exact diagonalization (Lanczos)",
      "bound_type": "exact",
      "bound_type_reason": "exact diagonalization of the full cluster; deterministic, exact to the printed digits (RULES.md 4)",
      "reference": "Lauchli, Sudan & Sorensen, Ground-state energy and spin gap of spin-1/2 kagome Heisenberg antiferromagnetic clusters: large-scale exact diagonalization results, Phys. Rev. B 83, 212401 (2011), arXiv:1103.1159",
      "peer_reviewed": true,
      "source": "exact-2026-09-15",
      "provenance": "primary",
      "verified": {
        "checked_on": "2026-09-15",
        "method": "arXiv PDF extracted locally with pypdf in layout mode, parsed by column position and checked against the paper's own per-site column; no LLM transcription",
        "reported_as": "Total E = -5.444875216 (S.S), cluster 12",
        "note": "Table I, \"Cluster studied in this work\", row N = 12: basis vectors a = (2,0), b = (0,2) in units of the kagome lattice vectors a1, a2 (each of length 2a), periodic (torus). E/N = -0.453740 as printed in the table's own E/N column; Pauli total = 4 E. The (2,0),(0,2) cluster is 2 x 2 unit cells, kagome-2x2 in the VarBench naming.",
        "secondary_of": null
      }
    }
  ],
  "url": "https://qmbl.org/i/Heisenberg/kagome-2x2_12_P/",
  "per_site_divisor": 48,
  "per_site_label": "E/N (S.S)",
  "record": null,
  "no_record_reason": "solved exactly"
}