{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"64d323b645c6225bc05ceeb0160df02a46f9bcdd66cbf4e257b39d67df77b6cb","created":"2026-10-03T07:18:00Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"b2406173c29abf2ec74aad304c0385ed3ccacfb08126ac646130e461163bae39","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"cm.hydrides.metallic-hydrogen-pressure","kind":"well-posed","literature_status":"contested","n":"1","parents":[],"plain":"Theory predicted in 1935 that squeezed hydrogen becomes a metal; experiments near 4 to 5 million atmospheres claim it, but the evidence is disputed.","posed_since":"1935","precise":"At $T < 100\\,\\mathrm{K}$, determine the pressure at which solid hydrogen becomes metallic and whether the transition goes from insulating molecular phase III to a metallic molecular phase or to atomic hydrogen. An answer combines infrared reflectivity showing a Drude response, dc electrical transport, and structure determination above $\\sim 4\\,\\mathrm{Mbar}$.","problem_ref":null,"references":"","settled_by":"Reproducible dc transport with metallic temperature dependence plus diffraction or Raman identification of the phase, at a stated calibrated pressure.","status_note":"Synchrotron infrared data (2020) showed a first-order gap collapse near 4.25 Mbar at about 80 K; the 2017 reflectivity claim at about 4.95 Mbar and dc confirmation remain disputed.","title":"At what pressure does solid hydrogen become a metal","topic_ref":"d8f6a90ffa2d9797ae166bd4e51b07a319dd484720f9647530fc1647474424b6"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"42c15a18bc4b06481b8dd555be03e60d83054a23ee3e605a8f3b7f1c0c586e13","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"0692c0de7fd8c5fd4529e06ad979c91cfedbd954df9dd898991899d5cde7eda1","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"Bccwbp_z9Oiwg_vP8HqoN-XkI_QlWE_LcZgZLbWLQ8gzD9UibEQWm-D_SeG6bbfNY-kVn2_7TuWFsHJeq1SSCA"},"schema":"pubphys.envelope/1"},"record_hash":"42c15a18bc4b06481b8dd555be03e60d83054a23ee3e605a8f3b7f1c0c586e13","leaf_index":1033}