The Journal of Physical Chemistry A最新文献

{"title":"Theoretical Study on Vibronically Resolved Spectra of Six Heteroatom-Doped Benzannulated [4]Helicenes: Vibrational Mode Assignments and Substituent Effects","authors":"Shiling Wang,&nbsp;Yanli Liu,&nbsp;Dongdong Yang,&nbsp;Meishan Wang,&nbsp;Yanliang Zhao,&nbsp;Qiushuang Xu","doi":"10.1021/acs.jpca.6c05271","DOIUrl":"10.1021/acs.jpca.6c05271","url":null,"abstract":"<p>Helicenederivatives have potential as chiral luminescent materials.However, the effect of substituents on the vibrational structuresof their spectra is not yet clear. In this work, we used time-dependent(TD) and time-independent (TI) methods to investigate the influenceof six heteroatom substituents (B, N, C, Si, P, and S) on the absorption(ABS), emission (EMI), circular dichroism, and circularly polarizedluminescence (CPL) spectra of [4]helicene derivatives. The resultsshow that the peak positions, the number of peaks, and their relativeintensities change systematically with the substituent. Clear vibrationalfine structures are observed for most derivatives. The only exceptionsare the EMI and CPL spectra of the S, Si, and P derivatives. Temperature-dependentcalculations show that the Si and P derivatives can recover vibrationalstructures at low temperature. We also assigned the vibrational modesof the ABS spectra using the TI method. By comparing the dimensionlessdisplacement parameters (δ), we systematically examined thesubstituent effect on vibronic activity. The assignments show thatthe displacement of low frequency torsional modes and the number ofmodes with significant displacement together affect the 0–0transition intensity. The number of high frequency ring stretchingmodes determines the richness of the vibrational fine structures.These results provide a direct vibrational assignment basis for understandingthe spectral behavior of helicene derivatives. They may also offertheoretical guidance for designing chiral luminescent materials withtunable spectral properties.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"130 43","pages":"8623–8632"},"PeriodicalIF":3.0,"publicationDate":"2026-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149293296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Theoretical Kinetic Study of the Reaction between CH3OȮ and ṄH2","authors":"Tingji Yao,&nbsp;Hao-Ting Guo,&nbsp;Yuxiang Zhu,&nbsp;Nadjib Rais,&nbsp;Henry J. Curran,&nbsp;Chong-Wen Zhou","doi":"10.1021/acs.jpca.6c04027","DOIUrl":"10.1021/acs.jpca.6c04027","url":null,"abstract":"<p>In NH₃/CH₄ combustion, the oxidationproductCH₃OȮ derived from ĊH₃ radicalscan react with abundant ṄH₂ radicals, and the CH₃OȮ + ṄH₂ ↔ CH₃Ȯ+ H₂NȮ reaction can significantly increase reactivityand influence the model-predicted ignition delay times of NH₃/CH₄ mixtures at low to intermediate temperatures. Inthis work, the detailed reaction kinetics between CH₃OȮand ṄH₂ and the subsequent unimolecular decompositionprocesses are investigated. High-level <em>ab initio</em> calculationsare performed for all species using the ANL0 method. Variable reactioncoordinate transition state theory (VRC-TST) is employed to treatthe barrierless radical–radical reaction channels, based ondirectly sampled interaction energies calculated at the CASPT2-F12/cc-pVTZ-F12level of theory, combined with one-dimensional (1-D) geometry andbasis set corrections. To properly describe the electronic structuresof different reaction channels, a (2e,2o) active space is employedfor the entrance channel of CH₃OȮ + ṄH₂ ↔ CH₃OONH₂, whereas a larger(6e,5o) active space is used for the dissociation reaction channelsof CH₃OONH₂ ↔ CH₃Ȯ+ H₂NȮ and CH₃ONH₂O ↔CH₃Ȯ + H₂NȮ. The reactive fluxesobtained are then coupled with Rice-Ramsperger-Kassel-Marcus/masterequation (RRKM/ME) calculations to calculate temperature- and pressure-dependentrate constants. The results indicate that the formation of CH₃Ȯ + H₂NȮ is the dominant reactionchannel. At the high-pressure limit (HPL), the dominant pathways forCH₃OONH₂ are isomerization to CH₃ONH₂O and dissociation to CH₃Ȯ + H₂NȮ. The CH₃ONH₂O isomer furtherdecomposes to CH₃Ȯ + H₂NȮ andbecomes the dominant pathway at <em>T</em> &gt; 1100 K. Thisstudy provides valuable kinetic parameters for CH₃OȮ+ ṄH₂, which is one of the key reactions in NH₃/CH₄ combustion in the temperature range 600−1500K.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"130 43","pages":"8677–8691"},"PeriodicalIF":3.0,"publicationDate":"2026-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149293238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrogenation of Uracil in Solid Para-Hydrogen: Infrared Spectra of Monohydrogenated Radicals (5H-C4H5N2O2, 6H-C4H5N2O2, and 4OH-C4H5N2O2) and Their Implications for RNA-Related Chemistry in the Interstellar Medium","authors":"Prasad Ramesh Joshi,&nbsp;Manish Kumar Tripathi,&nbsp;Yuan-Pern Lee","doi":"10.1021/acs.jpca.6c05066","DOIUrl":"10.1021/acs.jpca.6c05066","url":null,"abstract":"<p>Uracil (C₄H₄N₂O₂),an essential RNA nucleobase central to the RNA World hypothesis andthe prebiotic emergence of life, has been detected in pristine asteroidsamples, yet its survival mechanism in nonenergetic interstellar environmentsremains an elusive paradox. Backed by high-level CCSD(T)//B3LYP quantum-chemicalcalculations, we successfully captured and characterized the IR spectraof three transient, monohydrogenated radicals for the first time:the dominant 5<em>H</em>-C₄H₅N₂O₂<strong>(1)</strong> and minor 6<em>H</em>-C₄H₅N₂O₂<strong>(2)</strong> radicals,resulting from H-addition to the C═C moiety, alongside minorfeatures of the 4-hydroxy-uracil radical 4<em>OH</em>-C₄H₅N₂O₂<strong>(3)</strong>,resulting from H-addition to the carbonyl oxygen at the C4 position,under hydrogen-rich conditions. Under H-rich conditions, the formationof minor features of the dihydrogenated product 5,6-dihydrouracil(DHU), resulting via secondary H-addition to <strong>(1)</strong> or <strong>(2)</strong>, was also observed. The assignments for <strong>(3)</strong> and DHU are tentative because only a limited number of bands wereobserved due to low intensities and interference. Crucially, real-timetemporal profiling uncovered a striking, counterintuitive recyclingmechanism: while both secondary H-addition (forming DHU) and secondaryH-abstraction (regenerating uracil) are barrierless, the radical-to-parentregeneration pathway is significantly favored. This unexpected preferencesuggests that repeated collisions with cosmic hydrogen atoms mightnot efficiently destroy uracil, thereby drastically extending itschemical lifetime, which might have implications for how uracil couldsurvive and be exogenously seeded onto young planets.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"130 43","pages":"8597–8610"},"PeriodicalIF":3.0,"publicationDate":"2026-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149293235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Photocycloaddition Reaction and Excited-State Dynamics of Benzo[g]quinoxaline Derivatives Featuring X-Aggregated Dimers","authors":"Yan-Xiang Chen,&nbsp;Zi-Chen Liao,&nbsp;Xiao-Lan Li,&nbsp;Yu Wang,&nbsp;Bowei Ye,&nbsp;Jie-Ji Zhu,&nbsp;Shao-Fei Ni,&nbsp;Shun-Li Chen,&nbsp;Li Dang,&nbsp;Ming-De Li,&nbsp;Xin-Da Huang","doi":"10.1021/acs.jpca.6c05930","DOIUrl":"10.1021/acs.jpca.6c05930","url":null,"abstract":"<p>Reversible photocycloaddition reactions of anthracene-basedcompoundshave attracted considerable attention. However, the solid-state cycloadditionmechanism is unclear, and the cycloaddition behavior of X-aggregatedanthracene dimers remains unexplored. Herein, we found that 2,3-diethylbenzo[g]quinoxaline(<strong>EBQ</strong>), which assembles into crossing-stacked anthracenedimers with an −8.8° rotation angle, can undergo single-crystalto single-crystal photocycloaddition, accompanied by photochromismand fluorescence modulation. Detailed analyses via transient absorptionspectroscopy and theoretical calculation reveal that the solid-statecycloaddition of <strong>EBQ</strong> follows a stepwise mechanism: (1)fast structural arrangement from the localized S₁ stateto the delocalized excimer state upon photoexcitation; (2) intersystemcrossing via the S₁/T₂ crossing point; (3) formationof the first C–C bond via a rate-determining transition state,dominated by intermolecular steric hindrance; and (4) formation ofthe second C–C bond via the T₁/S₀ crossingpoint. Therefore, this work not only confirms the feasibility of thesolid-state photocycloaddition of X-aggregated anthracene dimers butalso elucidates the solid-state cycloaddition mechanism.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"130 43","pages":"8660–8667"},"PeriodicalIF":3.0,"publicationDate":"2026-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149293316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-Field Relaxation Dynamics of Parahydrogen-Hyperpolarized Propane Gas MRI Contrast Agent","authors":"Clementinah Oladun,&nbsp;Nuwandi M. Ariyasingha,&nbsp;Anna Samoilenko,&nbsp;Md Raduanul H. Chowdhury,&nbsp;Zhongjie Shi,&nbsp;Kehuan Luo,&nbsp;Sidhartha Tan,&nbsp;Oleg G. Salnikov,&nbsp;Dudari B. Burueva,&nbsp;Alba Xhupi,&nbsp;Majd Suleiman,&nbsp;Jerome McCreadie,&nbsp;Larisa M. Kovtunova,&nbsp;Igor V. Koptyug,&nbsp;Juri G. Gelovani,&nbsp;Panayiotis Nikolaou,&nbsp;Jessica Ettedgui,&nbsp;Rolf E. Swenson,&nbsp;Kazutoshi Yamamoto,&nbsp;Norikazu Koyasu,&nbsp;Murali C. Krishna,&nbsp;Joseph W. Plummer,&nbsp;Adrienne E. Campbell-Washburn,&nbsp;Michael J. Barlow,&nbsp;Boyd M. Goodson,&nbsp;Eduard Y. Chekmenev","doi":"10.1021/acs.jpca.6c05094","DOIUrl":"10.1021/acs.jpca.6c05094","url":null,"abstract":"<p>Hyperpolarized gas-phase MRI is an emerging diagnosticmodality,with the clinical utility of hyperpolarized Xe-129 gas for functionallung imaging recently supported by FDA regulatory approval. However,the requirement for dedicated multi-nuclear hardware and complex,centralized production logistics remains a significant translationalhurdle. Here, we investigate the longitudinal relaxation dynamicsof hyperpolarized propane gas─a promising, proton-frequencyalternative produced via heterogeneous parahydrogen-induced polarization(HET-PHIP)─across a wide range of magnetic field strengths:0.35 T, 0.55 T, 3 T, and 7 T MRI scanners. In the imaging studies,gradient-echo MRI pulse sequence variants with small flip angle excitationradio-frequency pulses were utilized to record a series of scans tomonitor the effective decay of the hyperpolarized state of propanegas in spherical plastic phantoms and excised rabbit lungs. We demonstratethat the effective lifetime (characterized by the constant of a mono-exponentialsignal decay <em>T</em>_d) of hyperpolarized propaneis strongly field-dependent, exhibiting a marked decrease from 1.51± 0.04 s (0.35 T) to 0.59 ± 0.02 s (0.55 T) to 0.54 ±0.02 s (3 T) to 0.23 ± 0.01 s (7 T) in phantom studies usingan RF flip angle of 5°. This trend is attributed to the presenceof partially retained long-lived spin states at the low field of 0.35T, which are quenched at higher field strengths as the spin systemtransitions from the strong-coupling to the weak-coupling regime.Moreover, the unfavorable spin-rotation dominated relaxation resultsin a further decrease of <em>T</em>_d at highermagnetic fields, especially evident at 7 T. Furthermore, we assessthe relaxation behavior in excised rabbit lungs at 0.35 T, reportinga <em>T</em>_d value of 0.68 ± 0.12 s. Thisaccelerated relaxation of hyperpolarized propane in the lung comparedto phantom models is likely driven by susceptibility-induced dephasingand increased surface-to-volume interactions within the alveolar architecture.The results using hyperpolarized propane were also compared with imagingstudies using hyperpolarized Xe-129 gas in the excised rabbit lungsat 0.35 T, yielding an effective ¹²⁹Xe <em>T</em>₁ of 11 ± 2 s. These results provide a fundamentalbiophysical characterization of hyperpolarized propane and underscoreits potential as a highly accessible contrast agent for regional pulmonaryfunction mapping.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"130 43","pages":"8611–8622"},"PeriodicalIF":3.0,"publicationDate":"2026-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149163550","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"E → Z Isomerization Catalyzed by Organic Photosensitizers Explored by Nonorthogonal Multireference Wave Function Methods","authors":"Saptarshi Saha,&nbsp;Saurav Parmar,&nbsp;Bholanath Maity,&nbsp;Luigi Cavallo,&nbsp;Lee M. Thompson,&nbsp;Pawel M. Kozlowski","doi":"10.1021/acs.jpca.6c05533","DOIUrl":"10.1021/acs.jpca.6c05533","url":null,"abstract":"<p>Triplet–triplet energy transfer (TEnT) processes,whereenergy is transferred from the triplet state of a donor (or photosensitizer,PS) to the singlet ground state of an acceptor (substrate), were appliedto investigate E → Z photocatalyzed isomerization of alkenes.Using Fermi’s golden rule and the four-state model, it wasdemonstrated that the rate of the catalytic cycle involving E-alkeneis faster, causing its depletion and conversely the accumulation ofZ-alkene. Three different systems have been investigated, namely styrenyl-silaneand styrenyl-boronate, using benzophenone as the PS, and the fluorenone/stilbenecomplex. The present study validates and generalizes a recently proposedtheoretical model for the mechanistic description of the preferentialaccumulation of the Z-isomer and depletion of the E-isomer. The quantitativesimilarities as well as the differences between the two currentlyinvestigated systems and the previously reported system were highlighted.Finally, the nonorthogonal multireference wave function approach wascompared with methods based on CAS-type wave functions using the benzophenone/styrenyl-silaneas the prototype system.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"130 43","pages":"8645–8659"},"PeriodicalIF":3.0,"publicationDate":"2026-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149293156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Active Thermochemical Tables: A Revision of the Enthalpy of Formation of Gas-Phase Sulfur Atom and a Refinement of the Thermochemistry of Several Other Key Sulfur Species","authors":"James H. Thorpe,&nbsp;David H. Bross,&nbsp;John F. Stanton,&nbsp;Jan M. L. Martin,&nbsp;Branko Ruscic","doi":"10.1021/acs.jpca.6c05060","DOIUrl":"10.1021/acs.jpca.6c05060","url":null,"abstract":"&lt;p&gt;Using the Active Thermochemical Tables (ATcT) approach,the 298.15K standard enthalpy of formation of sulfur atom has been revised to279.10 ± 0.12 kJ mol&lt;sup&gt;–1&lt;/sup&gt; (276.85 ± 0.12kJ mol&lt;sup&gt;–1&lt;/sup&gt; at 0 K). The new ATcT value is nearly 2kJ mol&lt;sup&gt;–1&lt;/sup&gt; higher than the original CODATA recommendation,with the difference being an order of magnitude larger than the combineduncertainties of the two. The CODATA value critically depends on pairingthe bond dissociation energy of gas-phase S&lt;sub&gt;2&lt;/sub&gt; with its enthalpyof formation. Early ATcT analyses involving a localized thermochemicalnetwork (TN) have strongly suggested that the observed predissociationsfrom the B &lt;sup&gt;3&lt;/sup&gt;Σ&lt;sub&gt;u&lt;/sub&gt;&lt;sup&gt;–&lt;/sup&gt; stateof S&lt;sub&gt;2&lt;/sub&gt;(g) and B &lt;sup&gt;3&lt;/sup&gt;Σ&lt;sup&gt;–&lt;/sup&gt; stateof SO(g) both refer to the ground-state limit, S (&lt;sup&gt;3&lt;/sup&gt;P&lt;sub&gt;2&lt;/sub&gt;) + S (&lt;sup&gt;3&lt;/sup&gt;P&lt;sub&gt;2&lt;/sub&gt;) and S (&lt;sup&gt;3&lt;/sup&gt;P&lt;sub&gt;2&lt;/sub&gt;) + O (&lt;sup&gt;3&lt;/sup&gt;P&lt;sub&gt;2&lt;/sub&gt;), respectively, rather thanthe excited S (&lt;sup&gt;3&lt;/sup&gt;P&lt;sub&gt;2&lt;/sub&gt;) + S (&lt;sup&gt;3&lt;/sup&gt;P&lt;sub&gt;1&lt;/sub&gt;) limit in S&lt;sub&gt;2&lt;/sub&gt;(g), as originally assumed by [ &lt;span&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;Ricks&lt;/span&gt;, &lt;span&gt;J. M.&lt;/span&gt;&lt;/span&gt;; &lt;span&gt;&lt;span&gt;Barrow&lt;/span&gt;, &lt;span&gt;R. F.&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;span&gt;Can. J.Phys.&lt;/span&gt;&lt;span&gt;1969&lt;/span&gt;, &lt;span&gt;47&lt;/span&gt;, &lt;span&gt;2423&lt;/span&gt;–&lt;span&gt;2427&lt;/span&gt;. &lt;span&gt; https://doi.org/10.1139/p69-297&lt;/span&gt;].&lt;/span&gt; and acceptedby CODATA, or the S (&lt;sup&gt;3&lt;/sup&gt;P&lt;sub&gt;2&lt;/sub&gt;) + O (&lt;sup&gt;3&lt;/sup&gt;P&lt;sub&gt;1&lt;/sub&gt;) limit in SO(g), as assumed by [ &lt;span&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;Clerbaux&lt;/span&gt;, &lt;span&gt;C.&lt;/span&gt;&lt;/span&gt;; &lt;span&gt;&lt;span&gt;Colin&lt;/span&gt;, &lt;span&gt;R.&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;span&gt;J. Mol. Spectrosc.&lt;/span&gt;&lt;span&gt;1994&lt;/span&gt;, &lt;span&gt;165&lt;/span&gt;, &lt;span&gt;334&lt;/span&gt;–&lt;span&gt;348&lt;/span&gt;. &lt;span&gt; https://doi.org/10.1006/jmsp.1994.1137&lt;/span&gt;].&lt;/span&gt;. For S&lt;sub&gt;2&lt;/sub&gt;(g), this was later experimentallyconfirmed by [ &lt;span&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;Frederix&lt;/span&gt;, &lt;span&gt;P. W. J. M.&lt;/span&gt;&lt;/span&gt;; et al.&lt;/span&gt;&lt;span&gt;J. Phys. Chem. A&lt;/span&gt;&lt;span&gt;2009&lt;/span&gt;, &lt;span&gt;113&lt;/span&gt;, &lt;span&gt;14995&lt;/span&gt;–&lt;span&gt;15005&lt;/span&gt;. &lt;span&gt; https://doi.org/10.1021/jp905104u&lt;/span&gt;].&lt;/span&gt;. The ATcT analyses also suggestedthat the CODATA enthalpy of formation of gas-phase S&lt;sub&gt;2&lt;/sub&gt; ismuch less robust than initially assumed. In contrast to the CODATAsingle-path provenance of the enthalpy of formation of sulfur atom,the distributed provenance of the ATcT value, which takes into accountthe sequential bond dissociation energies of SO&lt;sub&gt;2&lt;/sub&gt;(g) andH&lt;sub&gt;2&lt;/sub&gt;S(g), as well as thermochemical cycles involving sulfuricacid, suggests that the ATcT value is quite robust. The new enthalpyof formation of sulfur atom affects, &lt;em&gt;inter alia&lt;/em&gt;,all electronic structure computations that rely on converting thetheoretical total atomization energies to enthalpies of formation.In addition to providing a revised value for the enthalpy of formationof sulfur atom, ATcT also produces revised and improved enthalpiesof formation for nearly 200 sulfu","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"130 43","pages":"8576–8596"},"PeriodicalIF":3.0,"publicationDate":"2026-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149293206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Machine-Learning-Assisted Tuning of Exchange–Correlation Functional Parameters for the eXact-Integral Simplified Tamm-Dancoff Approximation Method","authors":"Sheng-Rui Wang,&nbsp;Dongyi Xiao,&nbsp;Qiu Fang,&nbsp;Xiang-Yang Liu,&nbsp;Ganglong Cui","doi":"10.1021/acs.jpca.6c04024","DOIUrl":"10.1021/acs.jpca.6c04024","url":null,"abstract":"<p>Here,we improve the accuracy of eXact-integral simplifiedTamm–Dancoffapproximation (XsTDA) excitation energies through reference-guidedand machine-learning-assisted molecule-specific tuning of exchange–correlationfunctional parameters in the XsTDA response calculation. Using DLPNO-STEOM-CCSDexcitation energies for 55,624 organic molecules, we systematicallytune one exchange–correlation functional parameter for fourhybrid functionals: the exact-exchange fraction <em>a</em>_<em>x</em> for PBE0 and M06–2X, and therange-separation parameter ω for CAM-B3LYP and ωB97X-D.Two objectives are considered, targeting either the first 10 singletexcited states or only S₁. With the standard functionalparameters, XsTDA yields 10-state MAEs of 0.61–0.97 eV relativeto DLPNO-STEOM-CCSD, whereas molecule-specific tuning reduces theseerrors to 0.19–0.28 eV. The two objectives reveal a clear one-parametertrade-off: S₁-specific tuning provides the highest S₁ accuracy but compromises higher excited states, whereas 10-statetuning gives more balanced multistate performance. To enable practicalapplication to new molecules, five machine-learning architecturesare trained to predict the tuned parameters directly from molecularstructure, yielding held-out-test MAEs of 0.21–0.30 eV forthe 10-state objective and 0.13–0.16 eV for the S₁-only objective. Among the models, a directed message-passing neuralnetwork shows the strongest overall transferability; combined withωB97X-D, it yields MAEs of 0.23 and 0.24 eV for the 10-stateand S₁-only objectives on the 32-molecule subset derivedfrom the original XsTDA benchmark. These results establish ML-assistedmolecule-specific parameter tuning as a practical route to improveXsTDA excitation energies while retaining its computational efficiency.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"130 43","pages":"8692–8706"},"PeriodicalIF":3.0,"publicationDate":"2026-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149293159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Symmetry- and Anharmonicity-Controlled Intramolecular Vibrational Energy Flow in Isolated Nitromethane: Ab Initio Molecular Dynamics Simulations","authors":"Juan Zhao,&nbsp;Jianping Wang","doi":"10.1021/acs.jpca.6c03084","DOIUrl":"10.1021/acs.jpca.6c03084","url":null,"abstract":"<p>Mode-specificintramolecular vibrational energy redistributionis a key elementary process in the earliest molecular response ofenergetic materials, yet a quantitative, mode-resolved descriptionof its microscopic driving forces remains challenging. Here we combinedensity functional theory (DFT), ab initio molecular dynamics (AIMD),normal-mode projection, spectral energy density analysis (SED), anda perturbative mode-coupling model to resolve vibrational energy flowin isolated nitromethane after selective excitation of individualnormal modes. The simulations reveal a nonrandom, hierarchical energy-flownetwork in which low- and midfrequency modes funnel energy towarda small set of accepting modes. Spectral fingerprints of acceptor-modemomenta show that most primary transfer channels are not fundamental-fundamentalresonances but overtone-fundamental resonances mediated by cubic anharmonicity.This mechanism naturally explains apparently cross-symmetry transfer:the overtone of an A″ mode transforms as A′ and cantherefore couple to A′ acceptor fundamentals. A simplifiedFermi’s Golden Rule model, parametrized by bilinear and third-orderanharmonic force constants and finite-time Lorentzian detuning factors,predicts the dominant primary acceptors observed in AIMD. The isolatedmolecule exhibits coherent quantum-beating-like energy oscillationswhose periods are governed by the detuning of the corresponding resonancecondition. These results recast vibrational energy transfer in nitromethaneas a symmetry-filtered anharmonic resonance network and provide atransferable framework for identifying early energy-flow bottlenecksin energetic molecules.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"130 43","pages":"8545–8556"},"PeriodicalIF":3.0,"publicationDate":"2026-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149293249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electron-Number Response of QTAIM Delocalization Indices: A Differential Decomposition into Population and Orbital-Relaxation Contributions","authors":"Samir Kenouche,&nbsp;Jorge I. Martìnez-Araya","doi":"10.1021/acs.jpca.6c05379","DOIUrl":"10.1021/acs.jpca.6c05379","url":null,"abstract":"<p>This work establishes a differential framework for analyzingtheelectron-number response of QTAIM delocalization indices within thepiecewise-linear ensemble formalism of conceptual density functionaltheory (C-DFT). The resulting first-order response is decomposed intothree distinct contributions: a population term arising from occupationnumber changes, an orbital relaxation term, and a geometric domainrelaxation term. The latter follows from the application of the Reynoldstransport theorem to QTAIM zero-flux domains and accounts for thedisplacement of atomic boundaries. The geometric contribution is expressedin terms of the normal velocity of the zero-flux surface. Assumingfixed QTAIM domains, the geometric contribution vanishes by construction,leading to a consistent operational partition of the delocalizationindex variation into population and orbital relaxation components.Applications to aromatic systems show that the electron-number responseof the delocalization index is governed by the interplay between occupationnumber and orbital relaxation effects, whose relative importance dependssensitively on both the molecular environment and the direction ofthe electron-number change.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"130 43","pages":"8633–8644"},"PeriodicalIF":3.0,"publicationDate":"2026-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149293188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}