Pub Date : 2025-02-10DOI: 10.1021/acs.jpca.5c00380
Beomgyu Kang, Bong June Sung
Measuring the combustion properties of potentially hazardous chemical compounds is critical to preparing safety guidelines or regulations but is often challenging and costly. Developing precise prediction models for the combustion properties is, therefore, an issue of importance in both industry and academy. Previous studies reported promising models based on graph neural networks (GNNs) and message-passing architectures. However, these models often neglect the hierarchical and three-dimensional structure of chemical compounds and do not provide chemical information like which fragments of the compound contribute to the combustion properties. In this study, we introduce Chemomile, an explainable geometry-based GNN model specifically designed for combustion property prediction. Chemomile constructs multiple graphs for each chemical compound using its molecular geometry: molecule-level, fragment-level, and junction-tree-level graphs. We employ multiple AttentiveFP layers for multiple graphs to make the final prediction of the combustion properties. Chemomile is optimized using particle swarm optimization (PSO) and benchmarked against five combustion properties (flashpoint, autoignition temperature, enthalpy of combustion, and upper and lower flammability limits). We use a perturbation-based explanation method to quantify the atom-wise contribution to the properties, thus providing valuable information on how the chemical structure and each atom influence the overall combustion properties.
{"title":"Chemomile: Explainable Multi-Level GNN Model for Combustion Property Prediction.","authors":"Beomgyu Kang, Bong June Sung","doi":"10.1021/acs.jpca.5c00380","DOIUrl":"https://doi.org/10.1021/acs.jpca.5c00380","url":null,"abstract":"<p><p>Measuring the combustion properties of potentially hazardous chemical compounds is critical to preparing safety guidelines or regulations but is often challenging and costly. Developing precise prediction models for the combustion properties is, therefore, an issue of importance in both industry and academy. Previous studies reported promising models based on graph neural networks (GNNs) and message-passing architectures. However, these models often neglect the hierarchical and three-dimensional structure of chemical compounds and do not provide chemical information like which fragments of the compound contribute to the combustion properties. In this study, we introduce Chemomile, an explainable geometry-based GNN model specifically designed for combustion property prediction. Chemomile constructs multiple graphs for each chemical compound using its molecular geometry: molecule-level, fragment-level, and junction-tree-level graphs. We employ multiple AttentiveFP layers for multiple graphs to make the final prediction of the combustion properties. Chemomile is optimized using particle swarm optimization (PSO) and benchmarked against five combustion properties (flashpoint, autoignition temperature, enthalpy of combustion, and upper and lower flammability limits). We use a perturbation-based explanation method to quantify the atom-wise contribution to the properties, thus providing valuable information on how the chemical structure and each atom influence the overall combustion properties.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143381132","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}
Pub Date : 2025-02-09DOI: 10.1021/acs.jpca.4c07189
YingXing Cheng
The static dipole polarizabilities of group 11 elements (Cu, Ag, and Au) are computed using the relativistic coupled-cluster method with single, double, and perturbative triple excitations. Three types of relativistic effects on dipole polarizabilities are investigated: scalar-relativistic, spin-orbit coupling (SOC), and fully relativistic Dirac-Coulomb contributions. The final recommended values, including uncertainties, are 46.91 ± 1.31 a.u. for Cu, 50.97 ± 1.93 a.u. for Ag, and 36.68 ± 0.78 a.u. for Au. Our results show close agreement with the values recommended in the 2018 table of static dipole polarizabilities for neutral elements [Mol. Phys.2019, 117, 1200], with reduced uncertainties for Ag and Au. The analysis indicates that scalar-relativistic effects are the dominant relativistic contribution for these elements, while SOC effects are negligible. The influence of electron correlation across all relativistic regimes is also evaluated, demonstrating its significant role in the accurate calculation of dipole polarizabilities.
{"title":"Relativistic and Electron-Correlation Effects in Static Dipole Polarizabilities for Group 11 Elements.","authors":"YingXing Cheng","doi":"10.1021/acs.jpca.4c07189","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c07189","url":null,"abstract":"<p><p>The static dipole polarizabilities of group 11 elements (Cu, Ag, and Au) are computed using the relativistic coupled-cluster method with single, double, and perturbative triple excitations. Three types of relativistic effects on dipole polarizabilities are investigated: scalar-relativistic, spin-orbit coupling (SOC), and fully relativistic Dirac-Coulomb contributions. The final recommended values, including uncertainties, are 46.91 ± 1.31 a.u. for Cu, 50.97 ± 1.93 a.u. for Ag, and 36.68 ± 0.78 a.u. for Au. Our results show close agreement with the values recommended in the 2018 table of static dipole polarizabilities for neutral elements [<i>Mol. Phys.</i> <b>2019</b>, 117, 1200], with reduced uncertainties for Ag and Au. The analysis indicates that scalar-relativistic effects are the dominant relativistic contribution for these elements, while SOC effects are negligible. The influence of electron correlation across all relativistic regimes is also evaluated, demonstrating its significant role in the accurate calculation of dipole polarizabilities.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143381135","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}
Pub Date : 2025-02-08DOI: 10.1021/acs.jpca.4c08499
Zhe Wang, Håkon Emil Kristiansen, Thomas Bondo Pedersen, T Daniel Crawford
In order to explore the effects of high levels of electron correlation on the real-time coupled cluster formalism and algorithmic behavior, we introduce a time-dependent implementation of the CC3 singles, doubles, and approximate triples method. We demonstrate the validity of our derivation and implementation using specific applications of frequency-dependent properties. Terms with triples are calculated and added to the existing CCSD equations, giving the method a nominal (N7) scaling. We also use a graphics processing unit accelerated implementation to reduce the computational cost, which we find can speed up the calculation by up to a factor of 13 for test cases of water clusters. In addition, we compare the impact of using single-precision arithmetic compared to conventional double-precision arithmetic. We find no significant difference in polarizabilities and optical-rotation tensor results but a somewhat larger error for first hyperpolarizabilities. Compared to linear response CC3 results, the percentage errors of RT-CC3 polarizabilities and RT-CC3 first hyperpolarizabilities are under 0.1 and 1%, respectively, for a water-molecule test case in a double-ζ basis set. Furthermore, we compare the dynamic polarizabilities obtained using RT-CC3, RT-CCSD, and time-dependent nonorthogonal orbital-optimized coupled cluster doubles (TDNOCCDs) in order to examine the performance of RT-CC3 and the orbital-optimization effect using a set of ten-electron systems.
{"title":"Real-Time Coupled Cluster Theory with Approximate Triples.","authors":"Zhe Wang, Håkon Emil Kristiansen, Thomas Bondo Pedersen, T Daniel Crawford","doi":"10.1021/acs.jpca.4c08499","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c08499","url":null,"abstract":"<p><p>In order to explore the effects of high levels of electron correlation on the real-time coupled cluster formalism and algorithmic behavior, we introduce a time-dependent implementation of the CC3 singles, doubles, and approximate triples method. We demonstrate the validity of our derivation and implementation using specific applications of frequency-dependent properties. Terms with triples are calculated and added to the existing CCSD equations, giving the method a nominal <math><mi>O</mi></math>(<i>N</i><sup>7</sup>) scaling. We also use a graphics processing unit accelerated implementation to reduce the computational cost, which we find can speed up the calculation by up to a factor of 13 for test cases of water clusters. In addition, we compare the impact of using single-precision arithmetic compared to conventional double-precision arithmetic. We find no significant difference in polarizabilities and optical-rotation tensor results but a somewhat larger error for first hyperpolarizabilities. Compared to linear response CC3 results, the percentage errors of RT-CC3 polarizabilities and RT-CC3 first hyperpolarizabilities are under 0.1 and 1%, respectively, for a water-molecule test case in a double-ζ basis set. Furthermore, we compare the dynamic polarizabilities obtained using RT-CC3, RT-CCSD, and time-dependent nonorthogonal orbital-optimized coupled cluster doubles (TDNOCCDs) in order to examine the performance of RT-CC3 and the orbital-optimization effect using a set of ten-electron systems.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143373461","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}
Pub Date : 2025-02-08DOI: 10.1021/acs.jpca.4c04649
M C Wilding, F Demmel, M Wilson
The diffusion of sodium and carbonate ions in molten sodium carbonate is investigated by quasi-elastic neutron scattering (QENS) at T = 1143 K. The quasi-elastic scattering at small wave vectors is dominated by diffusing sodium ions, and the derived self-diffusion coefficient of DNa = 4.5 × 10-5 cm2/s agrees well with previous tracer diffusion measurements. The quasi-elastic scattering from the carbonate anion is coherent, and the coherent scattering dominates the QENS signal at scattering vectors with a modulus greater than 1 Å-1. The line width of the coherent scattering function is used to obtain the diffusion coefficient of the carbonate anion at this temperature of DCO32- = 2.4 × 10-5 cm2/s, again in agreement with values from tracer diffusion studies. The results from this QENS measurement are larger compared with molecular dynamics simulations using a recently developed model, which introduces flexibility to the carbonate anion and allows charge to fluctuate across the anion. The model was improved concerning the melting point of the simulated liquid. Scaling the temperature in terms of this melting point is shown to bring the simulated and experimental diffusion coefficients into good agreement. The self-diffusion coefficients are consistent with those expected for a fragile liquid, and the changes in viscosity expected as the carbonate liquid is cooled are explained by the development of chains and complex structures that directly result from the flexibility of the anion introduced in this modeling approach. This simulation methodology can therefore be applied to further studies of complex molten salts.
{"title":"Diffusion in Molten Sodium Carbonate.","authors":"M C Wilding, F Demmel, M Wilson","doi":"10.1021/acs.jpca.4c04649","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c04649","url":null,"abstract":"<p><p>The diffusion of sodium and carbonate ions in molten sodium carbonate is investigated by quasi-elastic neutron scattering (QENS) at <i>T</i> = 1143 K. The quasi-elastic scattering at small wave vectors is dominated by diffusing sodium ions, and the derived self-diffusion coefficient of <i>D</i><sub>Na</sub> = 4.5 × 10<sup>-5</sup> cm<sup>2</sup>/s agrees well with previous tracer diffusion measurements. The quasi-elastic scattering from the carbonate anion is coherent, and the coherent scattering dominates the QENS signal at scattering vectors with a modulus greater than 1 Å<sup>-1</sup>. The line width of the coherent scattering function is used to obtain the diffusion coefficient of the carbonate anion at this temperature of <i>D</i><sub>CO<sub>3</sub><sup>2-</sup></sub> = 2.4 × 10<sup>-5</sup> cm<sup>2</sup>/s, again in agreement with values from tracer diffusion studies. The results from this QENS measurement are larger compared with molecular dynamics simulations using a recently developed model, which introduces flexibility to the carbonate anion and allows charge to fluctuate across the anion. The model was improved concerning the melting point of the simulated liquid. Scaling the temperature in terms of this melting point is shown to bring the simulated and experimental diffusion coefficients into good agreement. The self-diffusion coefficients are consistent with those expected for a fragile liquid, and the changes in viscosity expected as the carbonate liquid is cooled are explained by the development of chains and complex structures that directly result from the flexibility of the anion introduced in this modeling approach. This simulation methodology can therefore be applied to further studies of complex molten salts.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143373449","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}
Pub Date : 2025-02-07DOI: 10.1021/acs.jpca.4c06808
Claude-Bernard Paultre, Alexander M Mebel, Kevin E O'Shea
Perfluoroalkyl ether carboxylic acids (PFECA), which are replacements for legacy per- and polyfluorinated alkyl substances (PFAS), exhibit undesirable properties and often require thermal remediation. Detailed kinetic evaluation of the pyrolysis of PFECA was achieved computationally using density functional ωB97xD/6-311+G (d,p) to establish homolytic bond dissociation energies for the carboxylic acid and carboxylate forms of ∼90-100 kcal/mol and as low as 65 ± 3 kcal/mol, respectively. The negatively charged oxygenated radical products collapse with activation energies (Ea) of Ea(β-scission) ∼ 12-42 kcal/mol, Ea(1,2-F-shift) ∼ 24-47 kcal/mol, and Ea(oxygen atom-shift) ∼ 33-35 kcal/mol and enthalpies (ΔH) of ΔH(F-loss) ∼ 56-71 kcal/mol. The perfluoroalkoxyl radical intermediates transform via Ea(β scission) ∼ 2-9 kcal/mol and Ea(F-loss) ∼ 25-43 kcal/mol. The radical intermediates have lifetimes in the microsecond-to-nanosecond range at 1000 K and 1 atm, with some radicals stable for hours or even days with respect to the unimolecular processes. The results provide new fundamental thermodynamic and kinetic parameters for the partitioning of the degradation pathways of PFECA and establish specific structure-activity relationships of intermediates, leading to the final degradation products. These results are critical for modeling the thermal treatment of PFECA and related PFAS.
{"title":"Computational Study of the Gas-Phase Thermal Degradation and the Reaction Rate Coefficients of Perfluoroalkyl Ether Carboxylic Acids.","authors":"Claude-Bernard Paultre, Alexander M Mebel, Kevin E O'Shea","doi":"10.1021/acs.jpca.4c06808","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c06808","url":null,"abstract":"<p><p>Perfluoroalkyl ether carboxylic acids (PFECA), which are replacements for legacy per- and polyfluorinated alkyl substances (PFAS), exhibit undesirable properties and often require thermal remediation. Detailed kinetic evaluation of the pyrolysis of PFECA was achieved computationally using density functional ωB97xD/6-311+G (d,p) to establish homolytic bond dissociation energies for the carboxylic acid and carboxylate forms of ∼90-100 kcal/mol and as low as 65 ± 3 kcal/mol, respectively. The negatively charged oxygenated radical products collapse with activation energies (<i>E</i><sub>a</sub>) of <i>E</i><sub>a</sub>(β-scission) ∼ 12-42 kcal/mol, <i>E</i><sub>a</sub>(1,2-F-shift) ∼ 24-47 kcal/mol, and <i>E</i><sub>a</sub>(oxygen atom-shift) ∼ 33-35 kcal/mol and enthalpies (Δ<i>H</i>) of Δ<i>H</i>(F-loss) ∼ 56-71 kcal/mol. The perfluoroalkoxyl radical intermediates transform via <i>E</i><sub>a</sub>(β scission) ∼ 2-9 kcal/mol and <i>E</i><sub>a</sub>(F-loss) ∼ 25-43 kcal/mol. The radical intermediates have lifetimes in the microsecond-to-nanosecond range at 1000 K and 1 atm, with some radicals stable for hours or even days with respect to the unimolecular processes. The results provide new fundamental thermodynamic and kinetic parameters for the partitioning of the degradation pathways of PFECA and establish specific structure-activity relationships of intermediates, leading to the final degradation products. These results are critical for modeling the thermal treatment of PFECA and related PFAS.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143370114","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}
Pub Date : 2025-02-06Epub Date: 2025-01-27DOI: 10.1021/acs.jpca.4c07585
Jingbin Li, Zhefeng Wang, Han Wang
With the advancement of extreme ultraviolet (EUV) lithography technology, the demand for high-performance EUV photoresists has surged. Traditional photoresists struggle to meet the stringent requirements for increasingly smaller feature sizes in semiconductor manufacturing. Among emerging candidates, tin-based materials, particularly Sn12-oxo photoresists, have shown promise due to their superior EUV light absorption properties. Modifying these clusters offers a potential pathway to tailoring their properties for specific lithographic applications. In this study, we investigate the relationship between the photosensitivity of experimentally synthesized Sn12-oxo photoresists and their calculable parameters with quantum chemistry calculations. Key parameters such as bonding energies between metal atoms and organic ligands, molecular ionization potential, electrostatic potential, and HOMO-LUMO gap are identified as critical for predicting photosensitivity. While current research predominantly focuses on replacing counter-anions in Sn12-oxo clusters, there is limited exploration of modifications through the replacement of organic ligands. We examined the effects of electron-withdrawing and electron-donating groups as ligands on the Sn12-oxo cluster's ionization potential and Sn-ligand bonding energy. Our findings suggest a strategy for designing high-performance photoresists, thereby illuminating the path to discovering novel photoresist materials.
{"title":"Computational Study of Organotin Oxide Systems for Extreme Ultraviolet Photoresist.","authors":"Jingbin Li, Zhefeng Wang, Han Wang","doi":"10.1021/acs.jpca.4c07585","DOIUrl":"10.1021/acs.jpca.4c07585","url":null,"abstract":"<p><p>With the advancement of extreme ultraviolet (EUV) lithography technology, the demand for high-performance EUV photoresists has surged. Traditional photoresists struggle to meet the stringent requirements for increasingly smaller feature sizes in semiconductor manufacturing. Among emerging candidates, tin-based materials, particularly Sn<sub>12</sub>-oxo photoresists, have shown promise due to their superior EUV light absorption properties. Modifying these clusters offers a potential pathway to tailoring their properties for specific lithographic applications. In this study, we investigate the relationship between the photosensitivity of experimentally synthesized Sn<sub>12</sub>-oxo photoresists and their calculable parameters with quantum chemistry calculations. Key parameters such as bonding energies between metal atoms and organic ligands, molecular ionization potential, electrostatic potential, and HOMO-LUMO gap are identified as critical for predicting photosensitivity. While current research predominantly focuses on replacing counter-anions in Sn<sub>12</sub>-oxo clusters, there is limited exploration of modifications through the replacement of organic ligands. We examined the effects of electron-withdrawing and electron-donating groups as ligands on the Sn<sub>12</sub>-oxo cluster's ionization potential and Sn-ligand bonding energy. Our findings suggest a strategy for designing high-performance photoresists, thereby illuminating the path to discovering novel photoresist materials.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"1420-1428"},"PeriodicalIF":2.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143044905","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}
Atomically precise nanoclusters (NCs) are promising building blocks for designing materials and interfaces with unique properties. By incorporating heteroatoms into the core, the electronic and magnetic properties of NCs can be precisely tuned. To accurately predict these properties, density functional theory (DFT) is often employed, making the rigorous benchmarking of DFT results particularly important. In this study, we present a benchmarking approach based on metal chalcogenide NCs as a model system. We synthesized a series of bimetallic, iron-cobalt chalcogenide NCs [Co6-xFexS8(PEt3)6]+ (x = 0-6) (PEt = triethyl phosphine) and investigated the effect of heteroatoms in the octahedral metal chalcogenide core on their size and electronic properties. Using ion mobility-mass spectrometry (IM-MS), we observed a gradual increase in the collision cross section (CCS) with an increase in the number of Fe atoms in the core. DFT calculations combined with trajectory method CCS simulations successfully reproduced this trend, revealing that the increase in cluster size is primarily due to changes in metal-ligand bond lengths, while the electronic properties of the core remain largely unchanged. Moreover, this method allowed us to exclude certain multiplicity states of the NCs, as their CCS values were significantly different from those predicted for the lowest-energy structures. This study demonstrates that gas-phase IM-MS is a powerful technique for detecting subtle size differences in atomically precise NCs, which are often challenging to observe using conventional NC characterization methods. Accurate CCS measurements are established as a benchmark for comparison with theoretical calculations. The excellent correspondence between experimental data and theoretical predictions establishes a robust foundation for investigating structural changes of transition metal NCs of interest to a broad range of applications.
{"title":"Structural Changes in Metal Chalcogenide Nanoclusters Associated with Single Heteroatom Incorporation.","authors":"Xilai Li, Shana Havenridge, Habib Gholipour-Ranjbar, Dylan Forbes, Wyatt Crain, Cong Liu, Julia Laskin","doi":"10.1021/acs.jpca.4c07000","DOIUrl":"10.1021/acs.jpca.4c07000","url":null,"abstract":"<p><p>Atomically precise nanoclusters (NCs) are promising building blocks for designing materials and interfaces with unique properties. By incorporating heteroatoms into the core, the electronic and magnetic properties of NCs can be precisely tuned. To accurately predict these properties, density functional theory (DFT) is often employed, making the rigorous benchmarking of DFT results particularly important. In this study, we present a benchmarking approach based on metal chalcogenide NCs as a model system. We synthesized a series of bimetallic, iron-cobalt chalcogenide NCs [Co<sub>6-<i>x</i></sub>Fe<sub><i>x</i></sub>S<sub>8</sub>(PEt<sub>3</sub>)<sub>6</sub>]<sup>+</sup> (<i>x</i> = 0-6) (PEt = triethyl phosphine) and investigated the effect of heteroatoms in the octahedral metal chalcogenide core on their size and electronic properties. Using ion mobility-mass spectrometry (IM-MS), we observed a gradual increase in the collision cross section (CCS) with an increase in the number of Fe atoms in the core. DFT calculations combined with trajectory method CCS simulations successfully reproduced this trend, revealing that the increase in cluster size is primarily due to changes in metal-ligand bond lengths, while the electronic properties of the core remain largely unchanged. Moreover, this method allowed us to exclude certain multiplicity states of the NCs, as their CCS values were significantly different from those predicted for the lowest-energy structures. This study demonstrates that gas-phase IM-MS is a powerful technique for detecting subtle size differences in atomically precise NCs, which are often challenging to observe using conventional NC characterization methods. Accurate CCS measurements are established as a benchmark for comparison with theoretical calculations. The excellent correspondence between experimental data and theoretical predictions establishes a robust foundation for investigating structural changes of transition metal NCs of interest to a broad range of applications.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"1310-1317"},"PeriodicalIF":2.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143021251","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}
Pub Date : 2025-02-06Epub Date: 2025-01-28DOI: 10.1021/acs.jpca.4c08358
João G F Romeu, David A Dixon
The bonding and spectroscopic properties of LaX and AcX (X = O and F) diatomic molecules were studied by high-level ab initio CCSD(T) and SO-CASPT2 electronic structure calculations. Bond dissociation energies (BDEs) were calculated at the Feller-Peterson-Dixon (FPD) level. Potential energy curves and spectroscopic constants for the lowest-lying spin-orbit Ω states were obtained at the SO-CASPT2/aQ-DK level. A dense manifold of excited states was described for the monofluorides with the ground states well separated from the excited states. The spectroscopic parameters were in good agreement with those reported experimentally for LaO and LaF. For the diatomic molecules containing actinides, no experimental data of these parameters was found, but the results were consistent with other high-level calculations. The BDEs calculated at the FPD level were 791.3 (LaO), 705.2 (AcO), 650.0 (LaF), and 678.6 (AcF) kJ/mol. The NBO analysis showed that the monofluorides are essentially ionic, which explains why the BDE(AcF) is higher than BDE(LaF); for the monoxides, covalent contributions involving the d orbitals of the metal and the p orbitals of the oxygen are stronger for LaO than AcO, which explains the higher BDE for LaO. The bond orders are predicted to be 2 for LaF and AcF, 3 for AcO, and higher than 3 for LaO.
{"title":"Energetic and Electronic Properties of AcX and LaX (X = O and F).","authors":"João G F Romeu, David A Dixon","doi":"10.1021/acs.jpca.4c08358","DOIUrl":"10.1021/acs.jpca.4c08358","url":null,"abstract":"<p><p>The bonding and spectroscopic properties of LaX and AcX (X = O and F) diatomic molecules were studied by high-level ab initio CCSD(T) and SO-CASPT2 electronic structure calculations. Bond dissociation energies (BDEs) were calculated at the Feller-Peterson-Dixon (FPD) level. Potential energy curves and spectroscopic constants for the lowest-lying spin-orbit Ω states were obtained at the SO-CASPT2/aQ-DK level. A dense manifold of excited states was described for the monofluorides with the ground states well separated from the excited states. The spectroscopic parameters were in good agreement with those reported experimentally for LaO and LaF. For the diatomic molecules containing actinides, no experimental data of these parameters was found, but the results were consistent with other high-level calculations. The BDEs calculated at the FPD level were 791.3 (LaO), 705.2 (AcO), 650.0 (LaF), and 678.6 (AcF) kJ/mol. The NBO analysis showed that the monofluorides are essentially ionic, which explains why the BDE(AcF) is higher than BDE(LaF); for the monoxides, covalent contributions involving the d orbitals of the metal and the p orbitals of the oxygen are stronger for LaO than AcO, which explains the higher BDE for LaO. The bond orders are predicted to be 2 for LaF and AcF, 3 for AcO, and higher than 3 for LaO.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"1396-1410"},"PeriodicalIF":2.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143057494","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}
Pub Date : 2025-02-06Epub Date: 2025-01-23DOI: 10.1021/acs.jpca.4c06773
Charlotte N Stindt, Taegeun Jo, Jorn D Steen, Ben L Feringa, Stefano Crespi
Understanding and controlling molecular motions is of pivotal importance for designing molecular machinery and functional molecular systems, capable of performing complex tasks. Herein, we report a comprehensive theoretical study to elucidate the dynamic behavior of a bis(benzoxazole)-based overcrowded alkene displaying several coupled and uncoupled molecular motions. The benzoxazole moieties give rise to 4 different stable conformers that interconvert through single-bond rotations. By performing excited- and ground-state molecular dynamics simulations, DFT calculations, and NMR studies, we found that the photochemical E-Z isomerization of the central double bond of each stable conformer is directional and leads to a mixture of metastable isomers. This transformation is analogous to the classical Feringa-type molecular motors, with the notable difference that, during the photochemical isomerization and the subsequent thermal helix inversion (THI) steps, multiple possible pathways take place that involve single-bond rotations that can be both coupled and uncoupled to the rotation of the naphthyl half of the molecule.
{"title":"Computational Study on the Dynamics of a Bis(benzoxazole)-Based Overcrowded Alkene.","authors":"Charlotte N Stindt, Taegeun Jo, Jorn D Steen, Ben L Feringa, Stefano Crespi","doi":"10.1021/acs.jpca.4c06773","DOIUrl":"10.1021/acs.jpca.4c06773","url":null,"abstract":"<p><p>Understanding and controlling molecular motions is of pivotal importance for designing molecular machinery and functional molecular systems, capable of performing complex tasks. Herein, we report a comprehensive theoretical study to elucidate the dynamic behavior of a bis(benzoxazole)-based overcrowded alkene displaying several coupled and uncoupled molecular motions. The benzoxazole moieties give rise to 4 different stable conformers that interconvert through single-bond rotations. By performing excited- and ground-state molecular dynamics simulations, DFT calculations, and NMR studies, we found that the photochemical <i>E-Z</i> isomerization of the central double bond of each stable conformer is directional and leads to a mixture of metastable isomers. This transformation is analogous to the classical Feringa-type molecular motors, with the notable difference that, during the photochemical isomerization and the subsequent thermal helix inversion (THI) steps, multiple possible pathways take place that involve single-bond rotations that can be both coupled and uncoupled to the rotation of the naphthyl half of the molecule.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"1301-1309"},"PeriodicalIF":2.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143027473","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}
Pub Date : 2025-02-06Epub Date: 2025-01-26DOI: 10.1021/acs.jpca.4c08503
A J Barclay, A R W McKellar, C Lauzin, N Moazzen-Ahmadi
High resolution infrared spectra of water-CO2 dimers are further studied using tunable infrared sources to probe a pulsed slit jet supersonic expansion. The relatively weak transition of D2O-CO2 in the D2O ν1 fundamental region (≈2760 cm-1) is observed for the first time, as are various spectra of D2O-13CO2. Combination bands involving the intermolecular in plane geared bend (disrotatory) mode are observed for H2O-CO2 (≈1642, 2397 cm-1) in the H2O ν2 and CO2 ν3 regions, for HDO-CO2 (≈2761 cm-1) in the HDO ν3 region, and for D2O-CO2 (≈2386, 2705 and 2821 cm-1) in the CO2 ν3, D2O ν1, and D2O ν3 regions. A combination band involving the intermolecular in plane antigeared bend (conrotatory) mode is observed for D2O-13CO2 (≈2425 cm-1) in the CO2 ν3 region. And finally, a combination band involving the intermolecular twist (internal rotation) mode is observed for D2O-CO2 (≈2874 cm-1) in the D2O ν3 region. But this twist transition actually appears as two bands of similar intensity, separated by 2 cm-1, suggesting an "accidental" near-coincidence of the "real" combination state with a "dark" background state of the same symmetry. Intermolecular mode frequencies determined from the combination bands are in very good agreement with a recent theoretical calculation based on a high-level ab initio potential surface.
{"title":"New Infrared Spectra of the Water-CO<sub>2</sub> Complex: Determination of Four Intermolecular Modes and Test of a High-Level Potential Energy Surface.","authors":"A J Barclay, A R W McKellar, C Lauzin, N Moazzen-Ahmadi","doi":"10.1021/acs.jpca.4c08503","DOIUrl":"10.1021/acs.jpca.4c08503","url":null,"abstract":"<p><p>High resolution infrared spectra of water-CO<sub>2</sub> dimers are further studied using tunable infrared sources to probe a pulsed slit jet supersonic expansion. The relatively weak transition of D<sub>2</sub>O-CO<sub>2</sub> in the D<sub>2</sub>O ν<sub>1</sub> fundamental region (≈2760 cm<sup>-1</sup>) is observed for the first time, as are various spectra of D<sub>2</sub>O-<sup>13</sup>CO<sub>2</sub>. Combination bands involving the intermolecular in plane geared bend (disrotatory) mode are observed for H<sub>2</sub>O-CO<sub>2</sub> (≈1642, 2397 cm<sup>-1</sup>) in the H<sub>2</sub>O ν<sub>2</sub> and CO<sub>2</sub> ν<sub>3</sub> regions, for HDO-CO<sub>2</sub> (≈2761 cm<sup>-1</sup>) in the HDO ν<sub>3</sub> region, and for D<sub>2</sub>O-CO<sub>2</sub> (≈2386, 2705 and 2821 cm<sup>-1</sup>) in the CO<sub>2</sub> ν<sub>3</sub>, D<sub>2</sub>O ν<sub>1</sub>, and D<sub>2</sub>O ν<sub>3</sub> regions. A combination band involving the intermolecular in plane antigeared bend (conrotatory) mode is observed for D<sub>2</sub>O-<sup>13</sup>CO<sub>2</sub> (≈2425 cm<sup>-1</sup>) in the CO<sub>2</sub> ν<sub>3</sub> region. And finally, a combination band involving the intermolecular twist (internal rotation) mode is observed for D<sub>2</sub>O-CO<sub>2</sub> (≈2874 cm<sup>-1</sup>) in the D<sub>2</sub>O ν<sub>3</sub> region. But this twist transition actually appears as two bands of similar intensity, separated by 2 cm<sup>-1</sup>, suggesting an \"accidental\" near-coincidence of the \"real\" combination state with a \"dark\" background state of the same symmetry. Intermolecular mode frequencies determined from the combination bands are in very good agreement with a recent theoretical calculation based on a high-level ab initio potential surface.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"1411-1419"},"PeriodicalIF":2.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143044910","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}