{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"41e4130c2cc72846ab41631e82af4e4bc599015ba0b8601801861e3d3c2d0034","created":"2026-10-03T07:17:57Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"91db0eb42b4363ab668b49b2a4267ed38f63e5c2521bb42f192f6427bb3738c3","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"bio.electrolytes-confined.underscreening-origin","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"In dilute salt water, ions shield electric charges over a distance that shrinks as more salt is added. Force measurements show that in very concentrated salt solutions and liquid salts this shielding distance grows again and becomes surprisingly long, which theory and simulations mostly fail to reproduce.","posed_since":"2013","precise":"Surface-force measurements in aqueous NaCl above $\\sim 1\\, \\mathrm{M}$ and in ionic liquids find an exponentially decaying force with decay length $\\lambda_S$ that grows with concentration and reaches several nm, scaling as $\\lambda_S/\\lambda_D \\sim (a/\\lambda_D)^n$ with $n \\sim 3$, where $\\lambda_D$ is the Debye length and a the ion diameter. Liquid-state theory and molecular simulations of bulk electrolytes give $n \\sim 1 \\text{ to } 1.5$ and much smaller $\\lambda_S$. An answer is a bulk or interfacial mechanism that reproduces the measured magnitude and n, or a demonstration that the long decay is an artifact of specific surfaces or measurement conditions.","problem_ref":null,"references":"","settled_by":"Agreement between independent methods (surface forces on several substrates, bulk scattering, simulations at the same composition) on $\\lambda_{S}$ versus concentration, with a theory reproducing the result.","status_note":"A 2024 Chemical Physics Letters review lists the unresolved issues; some 2022 measurements between smooth silica surfaces found no anomalous decay, while a 2025 second-harmonic scattering study reported asymptotic underscreening in the bulk.","title":"Why measured screening lengths grow in concentrated electrolytes","topic_ref":"157a1ba9426f0d60e33212293f1b767b543732401ec3d0153c6ca684819a4974"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"4c63f4fad2b555ee6a3a0aac0a73b4acbbd4155e4f89515923baa810d98fd4d4","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"95b5e17f60256a65b253a761f1937cb51bca280b3bdafa5d20e2feba4a9b570d","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"CbED1a53vRwYkB1ejr3apbqF0HLZcN1m02ovlGSe8rfqAR7JwBE54JEzgU0f1pItNyEIhuyOCOfdikx8o-ixCQ"},"schema":"pubphys.envelope/1"},"record_hash":"4c63f4fad2b555ee6a3a0aac0a73b4acbbd4155e4f89515923baa810d98fd4d4","leaf_index":764}