{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"5909108a2aae1e396e825774ed7e96ddbc3e46dac6810eb369dfbba08a98fd74","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b","ea150b8f16f7eadb14fbfa2c8c9daa6bf94923174d4a61727893c235ca78829b"],"salt":"f135649ea3664c8159005fb605c15ee2d71ef0fa82eb3716bc1ae566b7506602","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"chem.reaction-dynamics.water-isotope-effects","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"Heavy water, in which hydrogen is replaced by deuterium, has its density maximum near 11 C instead of 4 C and is about 23 percent more viscous. These differences come only from the quantum motion of nuclei, so they test whether simulations treat that motion correctly.","posed_since":"","precise":"Using path-integral simulations on a potential of coupled-cluster quality not fitted to isotope data, compute the $\\mathrm{H_2O}$ to $\\mathrm{D_2O}$ shifts of the temperature of maximum density (277.13 K versus about 284.3 K), the melting temperature (273.15 K versus about 276.97 K) and the viscosity ratio at 298 K (about 1.23), and decompose each into the competing quantum effects (hydrogen-bond weakening by intermolecular zero-point motion versus strengthening by O-H stretch delocalization). An answer is computed shifts within 1 K and 5 percent of experiment with the decomposition.","problem_ref":"ea150b8f16f7eadb14fbfa2c8c9daa6bf94923174d4a61727893c235ca78829b","references":"","settled_by":"Converged path-integral free-energy and dynamics calculations on an ab initio-quality many-body potential compared with measured isotope shifts.","status_note":"","title":"Quantitative $\\mathrm{H_2O}$ versus $\\mathrm{D_2O}$ differences from first-principles quantum simulation","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"9c762c6c0b573ed2808fbea197093bd405f454e0f2d617f0cbcda040f1252bdb","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"26570b171859ee37b1e059acc7fb707bfcdd3098dc5c3d3b823ed71afff7623b","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"mK4IMfJR7MYNQul9KMZ1OWxwUrB95hxp23L8VO6UTlRMXE4mm5XqQ2wjPrHwcj2Yvwhlc6qDi2W7j213EY_ZAg"},"schema":"pubphys.envelope/1"},"record_hash":"9c762c6c0b573ed2808fbea197093bd405f454e0f2d617f0cbcda040f1252bdb","leaf_index":2684}