{
  "experiment": "species-swap corruption: geometry identical, labels exchanged",
  "date": "2026-08-06",
  "cases": {
    "NaCl": {
      "control_cif": "NaCl_Fm-3m_control.cif",
      "swapped_cif": "NaCl_species_swap.cif",
      "swap": "site 0 (Na at 0,0,0) <-> site 4 (Cl at 1/2,1/2,1/2)",
      "distance_multisets_identical": true,
      "sg_control": "Fm-3m (robust 0.01-1.0 A)",
      "sg_swapped": "Pm-3m (robust 0.01-1.0 A)",
      "card_verdict_swapped": "ALL PASS",
      "reference_matcher_swapped": {
        "max_displacement_A": 0.0,
        "n_above_0p5": 0
      },
      "bvs_swapped": "all sites |BVS| = 1.00 (blind)",
      "ewald_eV_per_atom": {
        "control": -4.4618,
        "swapped": -2.5983
      },
      "prototype_aware_match_swapped": "2/8 atoms 2.82 A from species-correct ideal sites (caught)",
      "chemistry_signal_in_card_data": "swapped Na site has 6 Na neighbors at 2.82 A; swapped Cl site has 6 Cl; same-species contacts appear at the heteroatomic bond distance"
    },
    "ZnS": {
      "control_cif": "ZnS_zincblende_control.cif",
      "swapped_cif": "ZnS_species_swap.cif",
      "swap": "Zn corner <-> S at (1/4,1/4,1/4)",
      "distance_multisets_identical": true,
      "sg_control": "F-43m (robust)",
      "sg_swapped": "R3m (robust)",
      "card_verdict_swapped": "ALL PASS (reference matcher errored: refined cell 24 vs 8 atoms)",
      "bvs_swapped": "all sites |BVS| = 2.00 (blind)",
      "ewald_eV_per_atom": {
        "control": -20.1378,
        "swapped": -14.0367
      }
    }
  },
  "conclusions": [
    "Species-swap corruption is invisible to every geometry gate and to BVS; it presents as a different robust space group (B1->Pm-3m, F-43m->R3m).",
    "The reference matcher is self-referential: it refines against the corrupted labeling and reports perfect agreement.",
    "Three catches: (a) same-species first-shell contacts in ionic compounds (already in card data, no gate reads it), (b) Ewald/Madelung energy penalty, (c) prototype-aware species-correct template matching when the expected type is declared.",
    "Antisite disorder is real physics (inverse spinels, olivines): a species-swap flag must remain an invitation to inspect, not a verdict."
  ]
}