{"state_type":"pith_open_graph_state","state_version":"1.0","pith_number":"pith:2011:DMILMI562U2J3QSYCBBVM7NM44","merge_version":"pith-open-graph-merge-v1","event_count":2,"valid_event_count":2,"invalid_event_count":0,"equivocation_count":0,"current":{"canonical_record":{"metadata":{"abstract_canon_sha256":"f5173be38937f579139bb5803da05b143b63188e6bd5453407ff38e18b8cc113","cross_cats_sorted":[],"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cond-mat.supr-con","submitted_at":"2011-03-01T09:04:09Z","title_canon_sha256":"492f814dfe034ced0ae62c2e0a128fe1f95b08f88d233793cc2eb8bb9a2aab12"},"schema_version":"1.0","source":{"id":"1103.0108","kind":"arxiv","version":3}},"source_aliases":[{"alias_kind":"arxiv","alias_value":"1103.0108","created_at":"2026-05-18T02:03:01Z"},{"alias_kind":"arxiv_version","alias_value":"1103.0108v3","created_at":"2026-05-18T02:03:01Z"},{"alias_kind":"doi","alias_value":"10.48550/arxiv.1103.0108","created_at":"2026-05-18T02:03:01Z"},{"alias_kind":"pith_short_12","alias_value":"DMILMI562U2J","created_at":"2026-05-18T12:26:26Z"},{"alias_kind":"pith_short_16","alias_value":"DMILMI562U2J3QSY","created_at":"2026-05-18T12:26:26Z"},{"alias_kind":"pith_short_8","alias_value":"DMILMI56","created_at":"2026-05-18T12:26:26Z"}],"graph_snapshots":[{"event_id":"sha256:ef414d4d2b1b6244a8fae390b64d2d3dbc587ee400fd46e9d6076566da870950","target":"graph","created_at":"2026-05-18T02:03:01Z","signer":{"key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signer_id":"pith.science","signer_type":"pith_registry"},"payload":{"graph_snapshot":{"author_claims":{"count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","strong_count":0},"builder_version":"pith-number-builder-2026-05-17-v1","claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"paper":{"abstract_excerpt":"The phonon spectrum of the high-pressure simple cubic phase of calcium, in the harmonic approx- imation, shows imaginary branches that make it mechanically unstable. In this letter, the phonon spectrum is recalculated using density-functional theory (DFT) ab initio methods fully including anharmonic effects up to fourth order at 50 GPa. Considering that perturbation theory cannot be employed with imaginary harmonic frequencies, a variational procedure based on the Gibbs- Bogoliubov inequality is used to estimate the renormalized phonon frequencies. The results show that strong quantum anharmon","authors_text":"Aitor Bergara, Bruno Rousseau, Ion Errea","cross_cats":[],"headline":"","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cond-mat.supr-con","submitted_at":"2011-03-01T09:04:09Z","title":"Anharmonic stabilization of the high-pressure simple cubic phase of calcium"},"references":{"count":0,"internal_anchors":0,"resolved_work":0,"sample":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1103.0108","kind":"arxiv","version":3},"verdict":{"created_at":null,"id":null,"model_set":{},"one_line_summary":"","pipeline_version":null,"pith_extraction_headline":"","strongest_claim":"","weakest_assumption":""}},"verdict_id":null}}],"author_attestations":[],"timestamp_anchors":[],"storage_attestations":[],"citation_signatures":[],"replication_records":[],"corrections":[],"mirror_hints":[],"record_created":{"event_id":"sha256:46eadd8b3bd23b8759f047382bf420ff729a7a4cfd10e423ea9ceac78902930c","target":"record","created_at":"2026-05-18T02:03:01Z","signer":{"key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signer_id":"pith.science","signer_type":"pith_registry"},"payload":{"attestation_state":"computed","canonical_record":{"metadata":{"abstract_canon_sha256":"f5173be38937f579139bb5803da05b143b63188e6bd5453407ff38e18b8cc113","cross_cats_sorted":[],"license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","primary_cat":"cond-mat.supr-con","submitted_at":"2011-03-01T09:04:09Z","title_canon_sha256":"492f814dfe034ced0ae62c2e0a128fe1f95b08f88d233793cc2eb8bb9a2aab12"},"schema_version":"1.0","source":{"id":"1103.0108","kind":"arxiv","version":3}},"canonical_sha256":"1b10b623bed5349dc2581043567dace71f84a3e184b0e0415a859c954398ce8a","receipt":{"algorithm":"ed25519","builder_version":"pith-number-builder-2026-05-17-v1","canonical_sha256":"1b10b623bed5349dc2581043567dace71f84a3e184b0e0415a859c954398ce8a","first_computed_at":"2026-05-18T02:03:01.852108Z","key_id":"pith-v1-2026-05","kind":"pith_receipt","last_reissued_at":"2026-05-18T02:03:01.852108Z","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","receipt_version":"0.3","signature_b64":"nK7+SIgw/4M6ar3cB0/5dvKJKR7SQtb6ZFf8/Lgp7wf4qCuzlQ6y+IDsiz7ll+oRa1zpCPIDK/CQMFfZ+EESCg==","signature_status":"signed_v1","signed_at":"2026-05-18T02:03:01.852816Z","signed_message":"canonical_sha256_bytes"},"source_id":"1103.0108","source_kind":"arxiv","source_version":3}}},"equivocations":[],"invalid_events":[],"applied_event_ids":["sha256:46eadd8b3bd23b8759f047382bf420ff729a7a4cfd10e423ea9ceac78902930c","sha256:ef414d4d2b1b6244a8fae390b64d2d3dbc587ee400fd46e9d6076566da870950"],"state_sha256":"49a7d8135f50327ecccd2f1cdc692973fb48a59d574ace16ce16cba82c44a5ea"}