LK-99

We have synthesised a modified lead apatite in which copper replaces some of the lead. We measure superconductivity with a critical temperature of at least 400 K (127 °C) at ambient pressure. We attribute it to a small structural distortion: the copper substitution shrinks the volume slightly, which we believe creates the conditions for superconductivity. We plan to announce it as the first room-temperature, ambient-pressure superconductor.

1. The synthesised material is a lead apatite in which copper has replaced part of the lead.empirical · supported
2. The measured signal is superconductivity arising in the copper-substituted apatite phase itself, at ambient pressure.empirical · contested · it breaks here
3. The superconducting critical temperature is at least 400 K (127 °C).empirical · unsupported
4. Copper substitution slightly shrinks the lattice volume, producing a small structural distortion.empirical · supported
5. That volume shrinkage and distortion is what creates the conditions for superconductivity.causal · unsupported
6. The result is strong enough to announce as the first room-temperature, ambient-pressure superconductor.normative · unsupported

More than one lens found a hole in claim 2, each on its own. That is a stronger signal than one lens alone.

1. The First Room-Temperature Ambient-Pressure SuperconductorLee et al. · 2023 · arXiv (Cornell University) · cited on claim 2, 3, 4, 5, 6 · doi:10.48550/arxiv.2307.12008
2. Single Crystal Growth Tricks and TreatsTanya et al. · 2022 · arXiv (Cornell University) · cited on claim 2 · doi:10.48550/arxiv.2209.09370
3. Oxide Room Temperature Superconductivity At Ambient Pressure: Computations and Experimental VerificationsIsikaku-Ironkwe · 2021 · Bulletin of the American Physical Society · cited on claim 6 · record
4. Room-Temperature Superconductivity in Yb/Lu Substituted Clathrate Hexahydrides under Moderate PressureDu et al. · 2022 · Research · cited on claim 6 · doi:10.34133/2022/9784309
5. The 2021 room-temperature superconductivity roadmapBoeri et al. · 2021 · Journal of Physics Condensed Matter · cited on claim 6 · doi:10.1088/1361-648x/ac2864
6. On the practical limits to substitutionAyres · 2006 · Ecological Economics · retrieved, not cited · doi:10.1016/j.ecolecon.2006.02.011
7. Study of the mechanisms of heavy metal sorption by mineral apatite: the feasibility of soil and ground water remediationRadoičić · 2010 · retrieved, not cited · doi:10.2298/bg20101005kaludjerovicradoicic
8. From Cu2S nanocrystals to Cu doped CdS nanocrystals through cation exchange: controlled synthesis, optical properties and their p-type conductivity researchLiu et al. · 2015 · Science China Materials · retrieved, not cited · doi:10.1007/s40843-015-0080-z
9. COMPILATION OF CRYSTAL GROWERS AND CRYSTAL GROWTH PROJECTS.Zoology & Connolly · 1972 · retrieved, not cited · doi:10.2172/4624081
10. Separation of Ag and Cu from Their Aqueous Thiosulfate Complexes by UV-C IrradiationHan et al. · 2019 · Metals · retrieved, not cited · doi:10.3390/met9111178
11. Modularity and Twinning in Mineral Crystal StructuresFerraris · 2021 · MDPI eBooks · retrieved, not cited · doi:10.3390/books978-3-0365-1916-6
12. Anion substitution in Perovskite related materials for fuel cell applicationsHancock · 2012 · University of Birmingham Institutional Research Archive (University of Birmingham) · retrieved, not cited · record
13. Chemo-sensors development based on low-dimensional codoped Mn2O3-ZnO nanoparticles using flat-silver electrodesRahman et al. · 2013 · Chemistry Central Journal · retrieved, not cited · doi:10.1186/1752-153x-7-60
14. Synthèse par ammonolyse et étude des propriétés de luminescence dans des oxynitrures de structure apatite dopés au cérium ou à l’europiumThomas · 2012 · HAL · retrieved, not cited · doi:10.70675/dcd28896zcfe1z4903zab71z21976b0f3f04

Proposed tests that haven’t run are the agenda for what comes next. Download them as a draft pre-registration, ready to edit and register on OSF.

Nothing in the evidence supplied refutes it, but nothing described yet separates superconductivity in the copper-substituted apatite from a secondary phase, an artifact or ordinary magnetism, and the only matching record (E2) restates the same claim with no independent replication.

It failed: Nature reports the impurity explanation. What would overturn the review’s reading: In the purer material, resistance does not fall to the instrument floor at the same temperature that flux expulsion appears; or that temperature does not move down under applied field; or zero-field-cooled shielding covers far less of the sample than the apatite's measured volume fraction; or the step shows heating-cooling hysteresis beyond the setup's thermal lag; or the signals weaken as the secondary phases are removed.

A paragraph for your methods section

We used Feynman (feynman.works), an AI research-review tool running on Claude Opus 5.5, to critique “LK-99” on 2026-11-01 (run agents-2026-11-01/superconductor). It reconstructed 6 claims, retrieved 14 published records dated no later than 2023-07-22, and raised 6 objections through reasoning frameworks drawn from the published work of Richard Feynman, Barbara McClintock and Karl Popper. Each citation in its output was checked against the records it retrieved, and we read every source we relied on. Its objections informed our analysis; the conclusions, and any errors, are our own.

The lenses

• Richard FeynmanPhysics & scientific method · 1948–1980What experiment would distinguish this explanation from a convincing story?
• Barbara McClintockGenetics & observation · 1931–1980What does the exception reveal that the average has hidden?
• Karl PopperPhilosophy of science · 1934–1980What conceivable observation would count against this claim?

BibTeX

@misc{feynman-agents-2026-11-01-superconductor,
  title = {{Feynman review: LK-99}},
  author = {{Feynman Works}},
  year = {2026},
  howpublished = {\url{https://www.feynman.works/pack/superconductor}},
  note = {Run agents-2026-11-01/superconductor, Claude Opus 5.5, 2026-11-01}
}

@article{lee2023first,
  title = {{The First Room-Temperature Ambient-Pressure Superconductor}},
  author = {Lee and others},
  year = {2023},
  journal = {arXiv (Cornell University)},
  doi = {10.48550/arxiv.2307.12008}
}

@article{tanya2022single,
  title = {{Single Crystal Growth Tricks and Treats}},
  author = {Tanya and others},
  year = {2022},
  journal = {arXiv (Cornell University)},
  doi = {10.48550/arxiv.2209.09370}
}

@article{isikaku2021oxide,
  title = {{Oxide Room Temperature Superconductivity At Ambient Pressure: Computations and Experimental Verifications}},
  author = {Isikaku-Ironkwe},
  year = {2021},
  journal = {Bulletin of the American Physical Society},
  url = {https://meetings.aps.org/Meeting/MAR21/Session/L47.14}
}

@article{du2022room,
  title = {{Room-Temperature Superconductivity in Yb/Lu Substituted Clathrate Hexahydrides under Moderate Pressure}},
  author = {Du and others},
  year = {2022},
  journal = {Research},
  doi = {10.34133/2022/9784309}
}

@article{boeri2021room,
  title = {{The 2021 room-temperature superconductivity roadmap}},
  author = {Boeri and others},
  year = {2021},
  journal = {Journal of Physics Condensed Matter},
  doi = {10.1088/1361-648x/ac2864}
}

Run agents-2026-11-01/superconductor on Claude Opus 5.5. The review is reproducible from its record: the claims, the records retrieved before 22 July 2023, and each lens’s card. https://www.feynman.works/pack/superconductor