{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,7]],"date-time":"2026-08-07T15:39:03Z","timestamp":1786117143512,"version":"build-2736575974"},"reference-count":26,"publisher":"American Chemical Society (ACS)","issue":"31","license":[{"start":{"date-parts":[[2026,7,25]],"date-time":"2026-07-25T00:00:00Z","timestamp":1784937600000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-029"},{"start":{"date-parts":[[2026,7,25]],"date-time":"2026-07-25T00:00:00Z","timestamp":1784937600000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-037"},{"start":{"date-parts":[[2026,7,25]],"date-time":"2026-07-25T00:00:00Z","timestamp":1784937600000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-045"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,8,6]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Agreement between experiment and calculation is indispensable for structural interpretation, but agreement alone does not identify the structure sampled by a measurement. When spectroscopic accuracy is sought, the measured observable may be a vibrational average around a minimum, a tunneling average, or an above-barrier average rather than the property of a single equilibrium geometry. Here we introduce a diagnostic framework that combines newly generated high-accuracy equilibrium structures, perturbative anharmonic corrections for regular modes, one-dimensional variational treatments of selected low-barrier coordinates, and isotope-resolved residual patterns to identify the structural object probed by rotational spectroscopy. The central result is that improved numerical agreement changes the interpretation of agreement itself: once equilibrium-structure errors are reduced to the few-milliangstrom scale required by high-resolution spectroscopy, the remaining discrepancies are no longer generic electronic-structure failures but signatures of the vibrational treatment, the chosen structural reference, or both. Distinct structural-assignment regimes then emerge from the combined isotope-resolved experiment\u2013theory residual pattern. The decisive numerical signatures are residual-collapse factors of 1.5\u201336 for minimum-connected systems, values larger than 5 for glycine conformer II and larger than 8 for malonaldehyde, with isotope balance recovered only after the appropriate dynamic averaging. Compact covalent frameworks remain minimum-connected, selected hydrogen-bond separations require higher structural levels, and glycine conformer II, malonaldehyde, and the formic acid dimer require dynamic comparison targets. Corannulene and corannulene\u2013water extend the diagnostic to symmetry and high-accuracy structural-parameter reduction in a noncovalent complex, while the example of the hyperfine coupling constants for the glycine radical shows that the same ambiguity is not confined to rotational constants. Agreement becomes chemically meaningful only after the nuclear-motion regime sampled by the experiment has been identified.<\/jats:p>","DOI":"10.1021\/acs.jpclett.6c01953","type":"journal-article","created":{"date-parts":[[2026,7,27]],"date-time":"2026-07-27T05:12:37Z","timestamp":1785129157000},"page":"8889-8897","source":"Crossref","is-referenced-by-count":0,"title":["Agreement Is\nNot Assignment: Dynamic Observables and\nthe Limits of Structural Validation"],"prefix":"10.1021","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6420-4107","authenticated-orcid":true,"given":"Vincenzo","family":"Barone","sequence":"first","affiliation":[{"name":"Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM) , via G. Giusti 9 , ,","place":["Firenze, Italy, 50121"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8140-5397","authenticated-orcid":true,"given":"Luigi","family":"Crisci","sequence":"additional","affiliation":[{"name":"Scuola Superiore Meridionale , Largo San Marcellino 10 , ,","place":["Napoli, Italy, 80138"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4506-3200","authenticated-orcid":true,"given":"Federico","family":"Lazzari","sequence":"additional","affiliation":[{"name":"Scuola Superiore Meridionale , Largo San Marcellino 10 , ,","place":["Napoli, Italy, 80138"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4504-853X","authenticated-orcid":true,"given":"Marco","family":"Mendolicchio","sequence":"additional","affiliation":[{"name":"Scuola Normale Superiore , Piazza dei Cavalieri 7 , ,","place":["Pisa, Italy, 56126"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lina","family":"Uribe","sequence":"additional","affiliation":[{"name":"Scuola Superiore Meridionale , Largo San Marcellino 10 , ,","place":["Napoli, Italy, 80138"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2026,7,25]]},"reference":[{"key":"2026080609084333100_cit1","doi-asserted-by":"publisher","first-page":"1419","DOI":"10.1002\/jcc.27312","article-title":"On the performance of composite schemes\nin determining equilibrium molecular structures","volume":"45","author":"Sahoo","year":"2024","journal-title":"J. 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Lett."},{"key":"2026080609084333100_cit6","doi-asserted-by":"publisher","first-page":"7376","DOI":"10.1021\/acs.jpclett.5c01823","article-title":"Composite Gradient\nSchemes for Accurate\nMolecular Geometries:A Flexible Interface and Hierarchical Optimization\nWorkflow","volume":"16","author":"Crisci","year":"2025","journal-title":"J. Phys. Chem. Lett."},{"key":"2026080609084333100_cit7","doi-asserted-by":"publisher","first-page":"5102","DOI":"10.1021\/acs.jctc.6c00317","article-title":"From Energies\nto Structures: PNO-F12\nGeometry Optimization of Large Molecules for Near-Spectroscopic Accuracy","volume":"22","author":"Crisci","year":"2026","journal-title":"J. Chem. Theory Comput."},{"key":"2026080609084333100_cit8","doi-asserted-by":"publisher","first-page":"034106","DOI":"10.1063\/1.4773581","article-title":"An Efficient and near Linear Scaling\nPair Natural Orbital Based Local\nCoupled Cluster Method","volume":"138","author":"Riplinger","year":"2013","journal-title":"J. Chem. 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Theory Comput."},{"key":"2026080609084333100_cit14","doi-asserted-by":"publisher","first-page":"2842","DOI":"10.1021\/acs.jctc.4c00023","article-title":"Unbiased Comparison Between Theoretical\nand Experimental\nMolecular Structures and Properties: Toward an Accurate Reduced-Cost\nEvaluation of Vibrational Contributions","volume":"20","author":"Mendolicchio","year":"2024","journal-title":"J.\nChem. Theory Comput."},{"key":"2026080609084333100_cit15","doi-asserted-by":"publisher","first-page":"1243","DOI":"10.1021\/acs.jctc.2c01143","article-title":"Benchmark\nStructures\nand Conformational Landscapes of Amino Acids in the Gas Phase: a Joint\nVenture of Machine Learning, Quantum Chemistry, and Rotational Spectroscopy","volume":"19","author":"Barone","year":"2023","journal-title":"J. Chem. Theory Comput."},{"key":"2026080609084333100_cit16","doi-asserted-by":"publisher","first-page":"1358","DOI":"10.1039\/C2CP43884D","article-title":"Glycine Conformers:\nA Never-Ending Story?","volume":"15","author":"Barone","year":"2013","journal-title":"Phys. Chem. Chem. Phys."},{"key":"2026080609084333100_cit17","doi-asserted-by":"publisher","first-page":"6296","DOI":"10.1021\/ja00411a005","article-title":"Microwave\nspectroscopic study of malonaldehyde","volume":"103","author":"Baughcum","year":"1981","journal-title":"J. Am.\nChem. Soc."},{"key":"2026080609084333100_cit18","doi-asserted-by":"publisher","first-page":"3027","DOI":"10.1021\/acs.jpca.6c01085","article-title":"Tests Demonstrate the Accuracy\nof the Qim-Reaction Path Hamiltonian for Double-Well Tunneling Splittings\nfor H-Atom Transfer","volume":"130","author":"Qu","year":"2026","journal-title":"J. Phys. Chem. 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