{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"eaee2029c3074238d7ba564c99f2315585335bfb05e62c027010e404b882e548","created":"2026-10-03T07:17:57Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"bfe5cdcf97fa3ca197e802609012d89d3fb103cd12eeebc68ea85e894741d7e4","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":"1","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 CaCO3 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":null,"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":"1380a85b09074fe5f36e74fddf9348a147e8d031ca52cae30320a53fa96359da"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"8c38f99dbac84c38ff3684baba136e42f4d1bfe78e1078f90f1d96eb90571eef","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"c5bd3bbea19546566d6b42af3cfff926437c764d8ae01679ee699263088d8ba7","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"nTNYDKQ4Kuaqwvr7zDiqBWiKOzoge2FA50NigqFsLHTfLNLnPMAmh3nO7A4zCu8MiEv4KneTHyinTQUUXuYtBg"},"schema":"pubphys.envelope/1"},"record_hash":"8c38f99dbac84c38ff3684baba136e42f4d1bfe78e1078f90f1d96eb90571eef","leaf_index":811}