{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"f3f25e47fafd0215a5f1560f75d105fe1a08005d40ba0d8de4c4b7f28d73922d","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["8c38f99dbac84c38ff3684baba136e42f4d1bfe78e1078f90f1d96eb90571eef","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"0a8daf657d100c9d7c553d1d8ece7baad21e49d00bd159b9839cc273398c5e8d","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"yes-no","assisted_by":[],"external_id":"bio.nucleation.prenucleation-clusters","kind":"well-posed","literature_status":"contested","n":"2","parents":[],"plain":"Experiments reported small, stable ion clusters in calcium carbonate solutions even before the solution is saturated, which classical theory forbids. Whether these clusters are truly stable or are short-lived precursors of a dense liquid phase is disputed.","posed_since":"2008","precise":"Clusters of about $20\\ \\mathrm{Angstrom}$ were reported in 2008 in undersaturated and supersaturated $\\mathrm{CaCO_3}$ solutions, with properties inconsistent with CNT. Determine whether they are thermodynamically stable solute species (negative formation free energy over a range of concentrations) or kinetically persistent ion associates or droplets of a dense liquid formed by liquid-liquid separation, from measured cluster size distributions and formation free energies versus concentration and pH.","problem_ref":"8c38f99dbac84c38ff3684baba136e42f4d1bfe78e1078f90f1d96eb90571eef","references":"","settled_by":"Quantitative measurement of the cluster size distribution and its concentration dependence, compared with free-energy calculations, showing stable solutes or metastable dense-liquid droplets.","status_note":"","title":"Do stable prenucleation clusters exist in calcium carbonate solutions?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"371be471ba928fa9c07e325dbd7b4101938d3020880824825ef73a489097c4df","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"a9b4425e923aa1dcd820f90ac099b222ed55ee9326df5a6cee4c87182b6bee3d","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"8Qj7y4MbyH7EUmeqsSoZwQavsmXFnyKlBSiH8KjzIuKyIFipOCDOL_jdXvaN-Pj6rytZPJ0i-pzQNOWu8YDQBw"},"schema":"pubphys.envelope/1"},"record_hash":"371be471ba928fa9c07e325dbd7b4101938d3020880824825ef73a489097c4df","leaf_index":2600}