1
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Collins EM, Raghavachari K. Stepping-Stone CBH: Benchmark and Application of a Multilayered Isodesmic-Based Correction Scheme. J Chem Theory Comput 2024; 20:3543-3550. [PMID: 38630625 DOI: 10.1021/acs.jctc.3c01330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/19/2024]
Abstract
We present a generalization of the connectivity-based hierarchy (CBH) of isodesmic-based correction schemes to a multilayered fragmentation platform for overall cost reduction while retaining high accuracy. The newly developed multilayered CBH approach, called stepping-stone CBH (SSCBH), is benchmarked on a diverse set of 959 medium-sized organic molecules. Applying SSCBH corrections to the PBEh-D3 density functional resulted in an average error of 0.76 kcal/mol for the full test set compared to accurate CCSD(T)-quality enthalpies and an even lower error of 0.44 kcal/mol on a subset containing only acyclic molecules. These results rival the traditional CBH-3 approach at a greatly reduced cost, allowing larger fragment corrections to be made at the MP2 level of theory rather than with G4. Our SSCBH approach will enable more widespread applications of CBH methods to a broader range of organic and biomolecular systems.
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Affiliation(s)
- Eric M Collins
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Krishnan Raghavachari
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
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2
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Monge-Palacios M, Wang Q, Alshaarawi A, Sepulveda ACC, Sarathy SM. Quantum chemistry and kinetics of hydrogen sulphide oxidation. Phys Chem Chem Phys 2024; 26:3219-3228. [PMID: 38193631 DOI: 10.1039/d3cp04535h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2024]
Abstract
A fundamental understanding of the acid gas (H2S and CO2) chemistry is key to efficiently implement the desulphurisation process and even the production of clean fuels such as hydrogen or syngas. In this work, we developed a new kinetic model for the pyrolysis and oxidation of hydrogen sulphide by merging two previously reported models with the goal of covering a wider range of conditions and including the effect of carbon dioxide. The resulting model, which consists of 75 species and 514 reactions, was used to conduct rate of production and sensitivity analysis in plug flow reactor simulations, and the results were used to determine the most prominent reactions in which hydrogen sulphide, molecular hydrogen, and sulphur monoxide are involved. The resulting list of important reactions was screened and the kinetics of three of them, i.e., SO2 + S2 → S2O + SO, S2O + S2 → S3 + SO, and SO + SH → S2 + OH, was found to warrant further investigation. With the goal of improving the accurancy of our new kinetic model, we carried out a robust quantum chemistry and Rice-Ramsperger-Kassel-Marcus master equation study to obtain, for the first time, the forward and reverse rate constants for those three reactions at temperatures and pressures of interest for combustion and atmospheric chemistry. This work is the first step of a kinetic study that is aimed at improving the understanding of the chemistry of the pyrolysis and oxidation of H2S, highlighting the importance of sulphur-sulphur interactions and providing a fundamental basis for future kinetic models of H2S not only in the field of combustion, but also in atmospheric chemistry.
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Affiliation(s)
- M Monge-Palacios
- King Abdullah University of Science and Technology, Thuwal (Makkah) 23955, Saudi Arabia.
| | - Q Wang
- King Abdullah University of Science and Technology, Thuwal (Makkah) 23955, Saudi Arabia.
| | - A Alshaarawi
- Exploration and Petroleum Engineering Center-Advanced Research Center (EXPEC ARC), Saudi Aramco, Dhahran 34465, Saudi Arabia
| | - A C Cavazos Sepulveda
- Exploration and Petroleum Engineering Center-Advanced Research Center (EXPEC ARC), Saudi Aramco, Dhahran 34465, Saudi Arabia
| | - S M Sarathy
- King Abdullah University of Science and Technology, Thuwal (Makkah) 23955, Saudi Arabia.
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3
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Deng DD, Long B. Quantitative kinetics of the atmospheric reaction between isocyanic acid and hydroxyl radicals: post-CCSD(T) contribution, anharmonicity, recrossing effects, torsional anharmonicity, and tunneling. Phys Chem Chem Phys 2023; 26:485-492. [PMID: 38079149 DOI: 10.1039/d3cp04385a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Hydroxyl radicals (OH) are the most important atmospheric oxidant, initiating atmospheric reactions for the chemical transformation of volatile organic compounds. Here, we choose the HNCO + OH reaction as a prototype reaction because it contains the fundamental reaction processes for OH radicals: H-abstraction reaction by OH and OH addition reaction. However, its kinetics are unknown under atmospheric conditions. We investigate the reaction of HNCO with OH by using the GMM(P).L method close to the accuracy of single, double, triple, and quadruple excitations and noniterative quintuple excitations with a complete basis set (CCSDTQ(P)/CBS) as benchmark results and a dual-level strategy for kinetics calculations. The calculated rate constant of HNCO + OH is in good agreement with the experimental data available at the temperatures between 620 and 2500 K. We find that the rate constant cannot be correctly obtained by using experimental data to extrapolate the atmospheric temperature ranges. We find that the post-CCSD(T) contribution is very large for the barrier height with the value of -0.85 kcal mol-1 for the H-abstraction reaction, while the previous investigations were done up to the CCSD(T) level. Moreover, we also find that recrossing effects, tunneling, torsional anharmonicity, and anharmonicity are important for obtaining quantitative kinetics in the OH + HNCO reaction.
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Affiliation(s)
- Dai-Dan Deng
- College of Physics and Mechatronic Engineering, Guizhou Minzu University, Guiyang 550025, China.
| | - Bo Long
- College of Physics and Mechatronic Engineering, Guizhou Minzu University, Guiyang 550025, China.
- College of Materials Science and Engineering, Guizhou Minzu University, Guiyang 550025, China
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4
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Molteni G, Ponti A. Is DFT Accurate Enough to Calculate Regioselectivity? The Case of 1,3-Dipolar Cycloaddition of Azide to Alkynes and Alkenes. Chemphyschem 2023; 24:e202300114. [PMID: 36896728 DOI: 10.1002/cphc.202300114] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 03/07/2023] [Accepted: 03/09/2023] [Indexed: 03/11/2023]
Abstract
The importance of regioselectivity in 1,3-dipolar cycloadditions (DCs) makes it surprising that no benchmarking study on this problem has appeared. We investigated whether DFT calculations are an accurate tool to predict the regioselectivity of uncatalyzed thermal azide 1,3-DCs. We considered the reaction between HN3 and 12 dipolarophiles, comprising ethynes HC≡C-R and ethenes H2 C=CH-R (R=F, OH, NH2 , Me, CN, CHO), which cover a broad range of electron demand and conjugation ability. We established benchmark data by the W3X protocol [complete-basis-set-extrapolated CCSD(T)-F12 energy with T-(T) and (Q) corrections and MP2-calculated core/valence and relativistic effects] and showed that core/valence effects and high-order excitations are important for accurate regioselectivity. Regioselectivities calculated using an extensive set of density functional approximations (DFAs) were compared with benchmark data. Range-separated and meta-GGA hybrids gave the best results. Good treatment of self-interaction and electron exchange are the key features for accurate regioselectivity. Dispersion correction slightly improves agreement with W3X results. The best DFAs provide the isomeric TS energy difference with an expected error ≈0.7 mh and errors ≈2 mh can occur. The isomer yield provided by the best DFA has an expected error of ±5 %, though errors up to 20 % are not rare. At present, an accuracy of 1-2 % is unfeasible but it seems that we are not far from achieving this goal.
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Affiliation(s)
- Giorgio Molteni
- Dipartimento di Chimica, Università degli Studi di Milano, Via C. Golgi 19, 20133, Milano, Italy
| | - Alessandro Ponti
- Istituto di Scienze e Tecnologie Chimiche "Giulio Natta", Consiglio Nazionale delle Ricerche, Via C. Golgi 19, 20133, Milano, Italy
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5
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Chan B, Karton A. Assessment of DLPNO-CCSD(T)-F12 and its use for the formulation of the low-cost and reliable L-W1X composite method. J Comput Chem 2022; 43:1394-1402. [PMID: 35709311 DOI: 10.1002/jcc.26892] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 03/28/2022] [Accepted: 04/28/2022] [Indexed: 02/03/2023]
Abstract
In the present study, we have investigated the performance of RIJCOSX DLPNO-CCSD(T)-F12 methods for a wide range of systems. Calculations with a high-accuracy option ["DefGrid3 RIJCOSX DLPNO-CCSD(T1 )-F12"] extrapolated to the complete-basis-set limit using the maug-cc-pV[D+d,T+d]Z basis sets provides fairly good agreements with the canonical CCSD(T)/CBS reference for a diverse set of thermochemical and kinetic properties [with mean absolute deviations (MADs) of ~1-2 kJ mol-1 except for atomization energies]. On the other hand, the low-cost "RIJCOSX DLPNO-CCSD(T)-F12D" option leads to substantial deviations for certain properties, notably atomization energies (MADs of up to tens of kJ mol-1 ). With the high-accuracy CBS approach, we have formulated the L-W1X method, which further includes a low-cost core-valence plus scalar-relativistic term. It shows generally good accuracy. For improved accuracies in specific cases, we advise replacing maug-cc-pV(n+d)Z with jun-cc-pV(n+d)Z for the calculation of electron affinities, and using well-constructed isodesmic-type reactions to obtain atomization energies. For medium-sized systems, DefGrid3 RIJCOSX DLPNO-CCSD(T1 )-F12 calculations are several times faster than the corresponding canonical computation; the use of the local approximations (RIJCOSX and DLPNO) leads to a better scaling than that for the canonical calculation (from ~6-7 down to ~2-4 for our test systems). Thus, the DefGrid3 RIJCOSX DLPNO-CCSD(T1 )-F12 method, and the L-W1X protocol that based on it, represent a useful means for obtaining accurate thermochemical quantities for larger systems.
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Affiliation(s)
- Bun Chan
- Graduate School of Engineering, Nagasaki University, Nagasaki, Japan
| | - Amir Karton
- School of Molecular Sciences, University of Western Australia, Perth, WA, Australia
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6
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Dandu NK, Assary RS, Redfern PC, Ward L, Foster I, Curtiss LA. Improving the Accuracy of Composite Methods: A G4MP2 Method with G4-like Accuracy and Implications for Machine Learning. J Phys Chem A 2022; 126:4528-4536. [PMID: 35786965 DOI: 10.1021/acs.jpca.2c01327] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
G4MP2 theory has proven to be a reliable and accurate quantum chemical composite method for the calculation of molecular energies using an approximation based on second-order perturbation theory to lower computational costs compared to G4 theory. However, it has been found to have significantly increased errors when applied to larger organic molecules with 10 or more nonhydrogen atoms. We report here on an investigation of the cause of the failure of G4MP2 theory for such larger molecules. One source of error is found to be the "higher-level correction (HLC)", which is meant to correct for deficiencies in correlation contributions to the calculated energies. This is because the HLC assumes that the contribution is independent of the element and the type of bonding involved, both of which become more important with larger molecules. We address this problem by adding an atom-specific correction, dependent on atom type but not bond type, to the higher-level correction. We find that a G4MP2 method that incorporates this modification of the higher-level correction, referred to as G4MP2A, becomes as accurate as G4 theory (for computing enthalpies of formation) for a test set of molecules with less than 10 nonhydrogen atoms as well as a set with 10-14 such atoms, the set of molecules considered here, with a much lower computational cost. The G4MP2A method is also found to significantly improve ionization potentials and electron affinities. Finally, we implemented the G4MP2A energies in a machine learning method to predict molecular energies.
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Affiliation(s)
- Naveen K Dandu
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439 United States.,Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439 United States.,Chemical Engineering Department, University of Illinois-Chicago, Chicago, Illinois 60607 United States
| | - Rajeev S Assary
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439 United States.,Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439 United States
| | - Paul C Redfern
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439 United States
| | - Logan Ward
- Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439 United States.,Data Science and Learning Division, Argonne National Laboratory, Lemont, Illinois 60439 United States
| | - Ian Foster
- Data Science and Learning Division, Argonne National Laboratory, Lemont, Illinois 60439 United States.,Department of Computer Science, University of Chicago, Chicago, Illinois 60637 United States
| | - Larry A Curtiss
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439 United States.,Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439 United States
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7
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Bakowies D. ATOMIC-2 Protocol for Thermochemistry. J Chem Theory Comput 2022; 18:4142-4163. [PMID: 35658473 DOI: 10.1021/acs.jctc.1c01272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
ATOMIC is a midlevel thermochemistry protocol that uses Pople's concept of bond separation reactions (BSRs) as a theoretical framework to reduce computational demands in the evaluation of atomization energies and enthalpies of formation. Various composite models are available that approximate bond separation energies at the complete-basis-set limit of all-electron CCSD(T), each balancing computational cost with achievable accuracy. Evaluated energies are then combined with very high-level, precomputed atomization energies of all auxiliary molecules appearing in the BSR to obtain the atomization energy of the molecule under study. ATOMIC-2 is a new version of the protocol that retains the overall concept and all previously defined composite models but improves on ATOMIC-1 in various other ways: Geometry optimization and zero-point-energy evaluation are performed at the density functional level (PBE0-D3/6-311G(d)), which shows significant computational savings and better accuracy than the previously employed RI-MP2/cc-pVTZ. The BSR framework is improved, using more accurate complete-basis-set (CBS) extrapolations toward the Full CI limit for the atomization energies of all auxiliary molecules. Finally, and most importantly, an error and uncertainty model termed ATOMIC-2um is added that estimates average bias and uncertainty for each of the atomization energy contributions that arise from the simplified treatment of some contributions to bond separation energies (CCSD(T)) and the neglect of others (such as higher order, scalar relativistic, or diagonal Born-Oppenheimer corrections) or from residual error in the energies of auxiliary molecules. Large and diverse benchmarks including up to 1179 molecules are used to evaluate necessary reference data and to correlate the observed error for each of the contributions with appropriate proxies that are available without additional quantum-chemical calculations for a particular molecule and represent its size and type. The implementation of ATOMIC-2 considers neutral, closed-shell molecules containing H, C, N, O, and F atoms; compared to ATOMIC-1, the framework has been extended to cover a few challenging but rare bond topologies. In comparison to highly accurate reference data for 184 molecules taken from the ATcT database (V. 1.122r), regular ATOMIC-2 shows noticeable underbinding, but the bias-corrected protocol ATOMIC-2um is found to be more accurate than either ATOMIC-1 or standard Gaussian-4 theory, and the uncertainty model is consistent with statistics of actually observed errors. Problems arising from ambiguous or challenging Lewis-valence structures defining BSRs are discussed, and computational efficiency is demonstrated. Computer code is made available to perform ATOMIC-2um analyses.
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Affiliation(s)
- Dirk Bakowies
- Institute of Physical Chemistry, Department of Chemistry, University of Basel, Klingelbergstraße 80, CH 4056 Basel, Switzerland
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8
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Chan B. Accurate Thermochemistry for Main-Group Elements up to Xenon with the W n-P34 Series of Composite Methods. J Chem Theory Comput 2021; 17:5704-5714. [PMID: 34410730 DOI: 10.1021/acs.jctc.1c00598] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In the present study, we introduce the accurate Wn-P34 quantum chemistry composite methods with applicability to heavy p-block elements up to xenon. For a set of thermochemical properties for prototypical third- and fourth-row species and for a diverse set of small light-main-group species, they show accuracies of ∼3 kJ mol-1 or better. Overall, the Wn-P34 methods are comparable in accuracy to Wn, with a widened applicability to heavier elements. We have used Wn-P34 to compile the P34 set of accurate thermochemical values for heavy p-block species, and we have applied this set to assess a wide range of lower-cost methods. The results of our assessment show that the G4(MP2)-XK composite method provides adequate treatments for these species, but several widely used double-hybrid density functional theory (DH-DFT) methods show uncharacteristically large deviations. In contrast, we find it presently surprising that some pure and hybrid DFT methods such as TPSS and SCANh perform quite well. We hope that our findings and new tools would facilitate the application of computational chemistry for heavy elements, of which the properties are yet to be broadly explored.
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Affiliation(s)
- Bun Chan
- Graduate School of Engineering, Nagasaki University, Bunkyo 1-14, Nagasaki 852-8521, Japan
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9
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Li H, Brémond E, Sancho-García JC, Adamo C. Pairing double hybrid functionals with a tailored basis set for an accurate thermochemistry of hydrocarbons. RSC Adv 2021; 11:26073-26082. [PMID: 35479441 PMCID: PMC9037073 DOI: 10.1039/d1ra04108h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 07/19/2021] [Indexed: 11/21/2022] Open
Abstract
A collection of five challenging datasets, including noncovalent interactions, reaction barriers and electronic rearrangements of medium-sized hydrocarbons, has been selected to verify the robustness of double-hybrid functionals used in conjunction with the small DH-SVPD basis set, especially developed for noncovalent interactions. The analysis is completed by other, more standard functionals, for a total of 17 models, including also empirical corrections for dispersion. The obtained results show that the chemical accuracy threshold, that is an error lower than 1.0 kcal mol−1, can be obtained by pairing the nonempirical PBE-QIDH functional with the DH-SVPD basis set, as well as by other semi-empirical functionals, such as DSD-PBEP86, using larger basis sets and empirical corrections. More in general, a significant improvement can be obtained using the DH-SVPD basis set with DHs, without resorting to any empirical corrections. This choice leads to a fast computational protocol that, avoiding any empirical potential, remains on a fully quantum ground. The pairing of the PBE-QIDH double-hybrid functional with a tailored split-valence basis set leads to a fast computational protocol for the accurate evaluation of hydrocarbon thermochemistry, without resorting to any empirical correction.![]()
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Affiliation(s)
- Hanwei Li
- Chimie ParisTech, PSL Research University, CNRS, Institute of Chemistry for Health and Life Sciences F-75005 Paris France
| | - Eric Brémond
- Université de Paris, ITODYS, CNRS F-75006 Paris France
| | | | - Carlo Adamo
- Chimie ParisTech, PSL Research University, CNRS, Institute of Chemistry for Health and Life Sciences F-75005 Paris France .,Institut Universitaire de France 103 Boulevard Saint Michel F-75005 Paris France
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10
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Li H, Tirri B, Brémond E, Sancho-García JC, Adamo C. Beyond Chemical Accuracy for Alkane Thermochemistry: The DH thermo Approach. J Org Chem 2021; 86:5538-5545. [PMID: 33822605 DOI: 10.1021/acs.joc.1c00058] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The so-called protobranching phenomenon, that is the greater stability of branched alkanes with respect to their linear isomers, represents an interesting challenge for approaches based on density functional theory (DFT), since it requires a balanced description of several electronic effects, including (intramolecular) dispersion forces. Here, we investigate this problem using a protocol recently developed based on double-hybrid functionals and a small basis set, DH-SVPD, suited for noncovalent interactions. The energies of bond separation reactions (BSR), defined on the basis of an isodesmic principle, are taken as reference properties for the evaluation of 15 DFT approaches. The obtained results show that error lower than the so-called "chemical accuracy" (<1.0 kcal/mol) can be obtained by the proposed protocol on both relative reaction energies and enthalpies. These results are then verified on the standard BSR36 data set and support the proposition of our computational protocol, named DHthermo, where any DH functional, such as PBE-QIDH or B2PLYP, provides accurate results when coupled to an empirical dispersion correction and the DH-SVPD basis set. This protocol not only gives subchemical accuracy on the thermochemistry of alkanes but it is extremely easy to use with common quantum-chemistry codes.
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Affiliation(s)
- Hanwei Li
- Chimie ParisTech, PSL Research University, CNRS, Institute of Chemistry for Health and Life Sciences, F-75005 Paris, France
| | - Bernardino Tirri
- Chimie ParisTech, PSL Research University, CNRS, Institute of Chemistry for Health and Life Sciences, F-75005 Paris, France
| | - Eric Brémond
- Université de Paris, ITODYS, CNRS, F-75006 Paris, France
| | | | - Carlo Adamo
- Chimie ParisTech, PSL Research University, CNRS, Institute of Chemistry for Health and Life Sciences, F-75005 Paris, France.,Institut Universitaire de France, 103 Boulevard Saint Michel, F-75005 Paris, France
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11
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Chan B. Fullerene Thermochemical Stability: Accurate Heats of Formation for Small Fullerenes, the Importance of Structural Deformation on Reactivity, and the Special Stability of C 60. J Phys Chem A 2020; 124:6688-6698. [PMID: 32786665 DOI: 10.1021/acs.jpca.0c04732] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We have used quantum chemistry computations, in conjunction with isodesmic-type reactions, to obtain accurate heats of formation (HoFs) for the small fullerenes C20 (2358.2 ± 8.0 kJ mol-1), C24 (2566.2 ± 7.6), and the lowest-energy isomers of C32 (2461.1 ± 15.4), C42 (2629.0 ± 20.5), and C54 (2686.2 ± 25.3). As part of this endeavor, we have also obtained accurate HoFs for several medium-sized molecules, namely 216.6 ± 1.4 for fulvene, 375.5 ± 1.5 for pentalene, 670.8 ± 2.9 for acepentalene, and 262.7 ± 2.5 for acenaphthylene. We combine the energies of the small fullerenes and previously obtained energies for larger fullerenes (from C60 to C6000) into a full picture of fullerene thermochemical stability. In general, the per-carbon energies can be reasonably approximated by the "R+D" model that we have previously developed [Chan et al. J. Chem. Theory Comput. 2019, 15, 1255-1264], which takes into account Resonance and structural Deformation factors. In a case study on C54, we find that most of the high-deformation-energy atoms correspond to the sites of the C-Cl bond in the experimentally captured C54Cl8. In another case study, we find that C60 has the lowest value for the maximum local-deformation energy when compared with similar-sized fullerenes, which is consistent with its "special stability". These results are indicative of structural deformation playing an important role in the reactivity of fullerenes.
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Affiliation(s)
- Bun Chan
- Graduate School of Engineering, Nagasaki University, Bunkyo 1-14, Nagasaki-shi, Nagasaki 852-8521, Japan
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12
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Dandu N, Ward L, Assary RS, Redfern PC, Narayanan B, Foster IT, Curtiss LA. Quantum-Chemically Informed Machine Learning: Prediction of Energies of Organic Molecules with 10 to 14 Non-hydrogen Atoms. J Phys Chem A 2020; 124:5804-5811. [PMID: 32539388 DOI: 10.1021/acs.jpca.0c01777] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
High-fidelity quantum-chemical calculations can provide accurate predictions of molecular energies, but their high computational costs limit their utility, especially for larger molecules. We have shown in previous work that machine learning models trained on high-level quantum-chemical calculations (G4MP2) for organic molecules with one to nine non-hydrogen atoms can provide accurate predictions for other molecules of comparable size at much lower costs. Here we demonstrate that such models can also be used to effectively predict energies of molecules larger than those in the training set. To implement this strategy, we first established a set of 191 molecules with 10-14 non-hydrogen atoms having reliable experimental enthalpies of formation. We then assessed the accuracy of computed G4MP2 enthalpies of formation for these 191 molecules. The error in the G4MP2 results was somewhat larger than that for smaller molecules, and the reason for this increase is discussed. Two density functional methods, B3LYP and ωB97X-D, were also used on this set of molecules, with ωB97X-D found to perform better than B3LYP at predicting energies. The G4MP2 energies for the 191 molecules were then predicted using these two functionals with two machine learning methods, the FCHL-Δ and SchNet-Δ models, with the learning done on calculated energies of the one to nine non-hydrogen atom molecules. The better-performing model, FCHL-Δ, gave atomization energies of the 191 organic molecules with 10-14 non-hydrogen atoms within 0.4 kcal/mol of their G4MP2 energies. Thus, this work demonstrates that quantum-chemically informed machine learning can be used to successfully predict the energies of large organic molecules whose size is beyond that in the training set.
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Affiliation(s)
- Naveen Dandu
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States.,Joint Center for Energy Storage Research (JCESR), Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Logan Ward
- Joint Center for Energy Storage Research (JCESR), Argonne National Laboratory, Lemont, Illinois 60439, United States.,Data Science and Learning Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Rajeev S Assary
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States.,Joint Center for Energy Storage Research (JCESR), Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Paul C Redfern
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Badri Narayanan
- Department of Mechanical Engineering, University of Louisville, Louisville, Kentucky 40292, United States
| | - Ian T Foster
- Joint Center for Energy Storage Research (JCESR), Argonne National Laboratory, Lemont, Illinois 60439, United States.,Data Science and Learning Division, Argonne National Laboratory, Lemont, Illinois 60439, United States.,Department of Computer Science, University of Chicago, Chicago, Illinois 60637, United States
| | - Larry A Curtiss
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States.,Joint Center for Energy Storage Research (JCESR), Argonne National Laboratory, Lemont, Illinois 60439, United States
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13
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Semidalas E, Martin JML. Canonical and DLPNO-Based G4(MP2)XK-Inspired Composite Wave Function Methods Parametrized against Large and Chemically Diverse Training Sets: Are They More Accurate and/or Robust than Double-Hybrid DFT? J Chem Theory Comput 2020; 16:4238-4255. [PMID: 32456427 PMCID: PMC7366511 DOI: 10.1021/acs.jctc.0c00189] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
The
large and chemically diverse GMTKN55 benchmark was used as
a training set for parametrizing composite wave function thermochemistry
protocols akin to G4(MP2)XK theory (Chan, B.; Karton, A.; Raghavachari,
K. J. Chem. Theory Comput. 2019, 15, 4478–4484). On account of their availability
for elements H through Rn, Karlsruhe def2 basis sets were employed.
Even after reparametrization, the GMTKN55 WTMAD2 (weighted mean absolute
deviation, type 2) for G4(MP2)-XK is actually inferior to that of
the best rung-4 DFT functional, ωB97M-V. By increasing the basis
set for the MP2 part to def2-QZVPPD, we were able to substantially
improve performance at modest cost (if an RI-MP2 approximation is
made), with WTMAD2 for this G4(MP2)-XK-D method now comparable to
the better rung-5 functionals (albeit at greater cost). A three-tier
approach with a scaled MP3/def2-TZVPP intermediate step, however,
leads to a G4(MP3)-D method that is markedly superior to even the
best double hybrids ωB97M(2) and revDSD-PBEP86-D4. Evaluating
the CCSD(T) component with a triple-ζ, rather than split-valence,
basis set yields only a modest further improvement that is incommensurate
with the drastic increase in computational cost. G4(MP3)-D and G4(MP2)-XK-D
have about 40% better WTMAD2, at similar or lower computational cost,
than their counterparts G4 and G4(MP2), respectively: detailed comparison
reveals that the difference lies in larger molecules due to basis
set incompleteness error. An E2/{T,Q} extrapolation and a CCSD(T)/def2-TZVP
step provided the G4-T method of high accuracy and with just three
fitted parameters. Using KS orbitals in MP2 leads to the G4(MP3|KS)-D
method, which entirely eliminates the CCSD(T) step and has no steps
costlier than scaled MP3; this shows a path forward to further improvements
in double-hybrid density functional methods. None of our final selections
require an empirical HLC correction; this cuts the number of empirical
parameters in half and avoids discontinuities on potential energy
surfaces. G4-T-DLPNO, a variant in which post-MP2 corrections are
evaluated at the DLPNO-CCSD(T) level, achieves nearly the accuracy
of G4-T but is applicable to much larger systems.
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Affiliation(s)
- Emmanouil Semidalas
- Department of Organic Chemistry, Weizmann Institute of Science, 7610001 Reḩovot, Israel
| | - Jan M L Martin
- Department of Organic Chemistry, Weizmann Institute of Science, 7610001 Reḩovot, Israel
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14
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Zhang W, Kong X, Liu S, Zhao Y. Multi‐coefficients correlation methods. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2020. [DOI: 10.1002/wcms.1474] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Wenna Zhang
- The Institute of Technological Sciences, Wuhan University Wuhan Hubei People's Republic of China
| | - Xirui Kong
- The Institute of Technological Sciences, Wuhan University Wuhan Hubei People's Republic of China
| | - Sheng Liu
- The Institute of Technological Sciences, Wuhan University Wuhan Hubei People's Republic of China
| | - Yan Zhao
- The Institute of Technological Sciences, Wuhan University Wuhan Hubei People's Republic of China
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan Hubei People's Republic of China
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15
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Bakowies D. Estimating Systematic Error and Uncertainty in Ab Initio Thermochemistry: II. ATOMIC(hc) Enthalpies of Formation for a Large Set of Hydrocarbons. J Chem Theory Comput 2019; 16:399-426. [DOI: 10.1021/acs.jctc.9b00974] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dirk Bakowies
- Institute of Physical Chemistry, Department of Chemistry, University of Basel, Klingelbergstr. 80, CH 4056 Basel, Switzerland
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16
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Bakowies D. Estimating Systematic Error and Uncertainty in Ab Initio Thermochemistry. I. Atomization Energies of Hydrocarbons in the ATOMIC(hc) Protocol. J Chem Theory Comput 2019; 15:5230-5251. [DOI: 10.1021/acs.jctc.9b00343] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Dirk Bakowies
- Institute of Physical Chemistry, Department of Chemistry, University of Basel, Klingelbergstr. 80, CH 4056 Basel, Switzerland
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17
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Chan B. The CUAGAU Set of Coupled-Cluster Reference Data for Small Copper, Silver, and Gold Compounds and Assessment of DFT Methods. J Phys Chem A 2019; 123:5781-5788. [PMID: 31241947 DOI: 10.1021/acs.jpca.9b03976] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have obtained benchmark data for a set of small molecular systems of Cu, Ag, and Au using coupled-cluster methods. Using this collection of reference data (that we termed the CUAGAU set) for assessing DFT-type methods, we find the MN15-L nonhybrid DFT to be cost-effective for geometry optimization [mean absolute deviation (MAD) in bond length = 0.20 Å], with an accuracy that is comparable to that for the double-hybrid (DH) DFT method DSD-PBEP86 (MAD = 0.19 Å). For the computation of thermochemical properties, among "conventional" (non-MP2-based) DFT methods, the best performance is found for the global-hybrid meta-GGA functional MN15, with an MAD of 11.4 kJ mol-1. We also find the nonhybrid method B97M-rV to have a reasonable performance (MAD = 14.4 kJ mol-1), and it may serve as a cost-effective means for qualitative study. If we look beyond conventional functionals, we find DSD-PBEP86 (MAD = 7.3 kJ mol-1) to be more accurate than even MN15. Nonetheless, this level of accuracy is still not sufficient for quantitative studies. In this regard, high-level wave function methods such as composite procedures that are based on coupled cluster are still indispensable for obtaining reliable reference data for transition-metal species.
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Affiliation(s)
- Bun Chan
- Graduate School of Engineering , Nagasaki University , Bunkyo 1-14 , Nagasaki 852-8521 , Japan
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18
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Chan B, Karton A, Raghavachari K. G4(MP2)-XK: A Variant of the G4(MP2)-6X Composite Method with Expanded Applicability for Main-Group Elements up to Radon. J Chem Theory Comput 2019; 15:4478-4484. [DOI: 10.1021/acs.jctc.9b00449] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Bun Chan
- Graduate School of Engineering, Nagasaki University, Bunkyo-machi 1-14, Nagasaki 852-8521, Japan
| | - Amir Karton
- School of Molecular Sciences, The University of Western Australia, Perth, WA 6009, Australia
| | - Krishnan Raghavachari
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
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19
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Narayanan B, Redfern PC, Assary RS, Curtiss LA. Accurate quantum chemical energies for 133 000 organic molecules. Chem Sci 2019; 10:7449-7455. [PMID: 31489167 PMCID: PMC6713865 DOI: 10.1039/c9sc02834j] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 06/18/2019] [Indexed: 01/09/2023] Open
Abstract
The energies of the 133 000 molecules in the GDB-9 database have been calculated at the G4MP2 level of theory and then were used to calculate their enthalpies of formation.
The energies of the 133 000 molecules in the GDB-9 database have been calculated at the G4MP2 level of theory and then were used to calculate their enthalpies of formation. This database contains organic molecules having nine or less atoms of carbon, nitrogen, oxygen, and fluorine, as well as hydrogen atoms. The accuracy of the G4MP2 energies was investigated on a subset of 459 of the molecules having experimental enthalpies of formation with small uncertainties. On this subset the G4MP2 enthalpies of formation have an accuracy of 0.79 kcal mol–1, which is similar to its accuracy previously reported for the smaller G3/05 test set. An error analysis of the theoretical enthalpies of formation of the 459 molecules is presented in terms of the size and type of the molecules. Three different density functionals (B3LYP, ωB97X-D, M06-2X) were also assessed on 459 molecules of accurate enthalpy data for comparison with the G4MP2 results. The G4MP2 energies for the 133 K molecules provide a database that can be used to calculate accurate reaction energies as well as to assess new or existing experimental enthalpies of formation. Several examples are given of types of reactions that can be predicted using the G4MP2 database of energies. The G4MP2 energies of the GDB-9 molecules will also be useful in future investigations of applications of machine learning to quantum chemical data.
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Affiliation(s)
- Badri Narayanan
- Department of Mechanical Engineering , University of Louisville , Louisville , Kentucky 40292 , USA.,Materials Science Division , Argonne National Laboratory , Argonne , Illinois 60439 , USA .
| | - Paul C Redfern
- Materials Science Division , Argonne National Laboratory , Argonne , Illinois 60439 , USA .
| | - Rajeev S Assary
- Materials Science Division , Argonne National Laboratory , Argonne , Illinois 60439 , USA .
| | - Larry A Curtiss
- Materials Science Division , Argonne National Laboratory , Argonne , Illinois 60439 , USA .
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20
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Welch BK, Dawes R, Bross DH, Ruscic B. An Automated Thermochemistry Protocol Based on Explicitly Correlated Coupled-Cluster Theory: The Methyl and Ethyl Peroxy Families. J Phys Chem A 2019; 123:5673-5682. [DOI: 10.1021/acs.jpca.9b04381] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Bradley K. Welch
- Department of Chemistry, Missouri University of Science and Technology, Rolla, Missouri 65409, United States
| | - Richard Dawes
- Department of Chemistry, Missouri University of Science and Technology, Rolla, Missouri 65409, United States
| | - David H. Bross
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Branko Ruscic
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
- Consortium for Advanced Science and Engineering, University of Chicago, Chicago, Illinois 60637, United States
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21
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Zhao Y, Xia L, Liao X, He Q, Zhao MX, Truhlar DG. Extrapolation of high-order correlation energies: the WMS model. Phys Chem Chem Phys 2018; 20:27375-27384. [PMID: 30357169 DOI: 10.1039/c8cp04973d] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have developed a new composite model chemistry method called WMS (Wuhan-Minnesota scaling method) with three characteristics: (1) a composite scheme to approximate the complete configuration interaction valence energy with the affordability condition of requiring no calculation more expensive than CCSD(T)/jul-cc-pV(T+d)Z, (2) low-cost methods for the inner-shell correlation contribution and scalar relativistic correction, and (3) accuracy comparable to methods with post-CCSD(T) components. The new method is shown to be accurate for the W4-17 database of 200 atomization energies with an average mean unsigned error (averaged with equal weight over strongly correlated and weakly correlated subsets of the data) of 0.45 kcal mol-1, and the performance/cost ratio of these results compares very favorably to previously available methods. We also assess the WMS method against the DBH24-W4 database of diverse barrier heights and the energetics of the reactions of three strongly correlated Criegee intermediates with water. These results demonstrate that higher-order correlation contributions necessary to obtain high accuracy for molecular thermochemistry may be successfully extrapolated from the lower-order components of CCSD(T) calculations, and chemical accuracy can now be obtained for larger and more complex molecules and reactions.
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Affiliation(s)
- Yan Zhao
- State Key Laboratory of Silicate Materials for Architectures, International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, People's Republic of China.
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22
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Chan B, Kawashima Y, Hirao K. The reHISS Three-Range Exchange Functional with an Optimal Variation of Hartree-Fock and Its Use in the reHISSB-D Density Functional Theory Method. J Comput Chem 2018; 40:29-38. [DOI: 10.1002/jcc.25383] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 06/01/2018] [Accepted: 06/01/2018] [Indexed: 11/11/2022]
Affiliation(s)
- Bun Chan
- Graduate School of Engineering; Nagasaki University; Bunkyo 1-14, Nagasaki-shi, Nagasaki 852-8521 Japan
| | - Yukio Kawashima
- RIKEN Advanced Institute for Computational Science; 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe Hyogo 650-0047 Japan
| | - Kimihiko Hirao
- RIKEN Advanced Institute for Computational Science; 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe Hyogo 650-0047 Japan
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23
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Mallick S, Kumar P. Impact of Post-CCSD(T) Corrections on Reaction Energetics and Rate Constants of the OH• + HCl Reaction. J Phys Chem A 2018; 122:7151-7159. [DOI: 10.1021/acs.jpca.8b06092] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Pradeep Kumar
- Department of Chemistry, MNIT Jaipur, Jaipur 302017, India
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24
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Martin JML, Sylvetsky N. A simple model for scalar relativistic corrections to molecular total atomisation energies. Mol Phys 2018. [DOI: 10.1080/00268976.2018.1509147] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Jan M. L. Martin
- Department of Organic Chemistry, Weizmann Institute of Science, Reḥovot, Israel
| | - Nitai Sylvetsky
- Department of Organic Chemistry, Weizmann Institute of Science, Reḥovot, Israel
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25
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Ganyecz Á, Kállay M, Csontos J. High Accuracy Quantum Chemical and Thermochemical Network Data for the Heats of Formation of Fluorinated and Chlorinated Methanes and Ethanes. J Phys Chem A 2018; 122:5993-6006. [PMID: 29939026 DOI: 10.1021/acs.jpca.8b00614] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reliable heats of formation are reported for numerous fluorinated and chlorinated methane and ethane derivatives by means of an accurate thermochemical protocol, which involves explicitly correlated coupled-cluster calculations augmented with anharmonic, scalar relativistic, and diagonal Born-Oppenheimer corrections. The theoretical results, along with additional experimental data, are further enhanced with the help of the thermochemical network approach. For 28 species, out of 50, this study presents the best estimates, and discrepancies with previous reports are also highlighted. Furthermore, the effects of the less accurate theoretical data on the results yielded by thermochemical networks are discussed.
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Affiliation(s)
- Ádám Ganyecz
- MTA-BME Lendület Quantum Chemistry Research Group, Department of Physical Chemistry and Materials Science , Budapest University of Technology and Economics , P.O. Box 91, Budapest , H-1521 Hungary
| | - Mihály Kállay
- MTA-BME Lendület Quantum Chemistry Research Group, Department of Physical Chemistry and Materials Science , Budapest University of Technology and Economics , P.O. Box 91, Budapest , H-1521 Hungary
| | - József Csontos
- MTA-BME Lendület Quantum Chemistry Research Group, Department of Physical Chemistry and Materials Science , Budapest University of Technology and Economics , P.O. Box 91, Budapest , H-1521 Hungary
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26
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Chan B. Formulation of Small Test Sets Using Large Test Sets for Efficient Assessment of Quantum Chemistry Methods. J Chem Theory Comput 2018; 14:4254-4262. [DOI: 10.1021/acs.jctc.8b00514] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Bun Chan
- Graduate School of Engineering, Nagasaki University, Bunkyo 1-14, Nagasaki 852-8521, Japan
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27
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Long B, Bao JL, Truhlar DG. Unimolecular reaction of acetone oxide and its reaction with water in the atmosphere. Proc Natl Acad Sci U S A 2018; 115:6135-6140. [PMID: 29844185 PMCID: PMC6004451 DOI: 10.1073/pnas.1804453115] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Criegee intermediates (i.e., carbonyl oxides with two radical sites) are known to be important atmospheric reagents; however, our knowledge of their reaction kinetics is still limited. Although experimental methods have been developed to directly measure the reaction rate constants of stabilized Criegee intermediates, the experimental results cover limited temperature ranges and do not completely agree well with one another. Here we investigate the unimolecular reaction of acetone oxide [(CH3)2COO] and its bimolecular reaction with H2O to obtain rate constants with quantitative accuracy comparable to experimental accuracy. We do this by using CCSDT(Q)/CBS//CCSD(T)-F12a/DZ-F12 benchmark results to select and validate exchange-correlation functionals, which are then used for direct dynamics calculations by variational transition state theory with small-curvature tunneling and torsional and high-frequency anharmonicity. We find that tunneling is very significant in the unimolecular reaction of (CH3)2COO and its bimolecular reaction with H2O. We show that the atmospheric lifetimes of (CH3)2COO depend on temperature and that the unimolecular reaction of (CH3)2COO is the dominant decay mode above 240 K, while the (CH3)2COO + SO2 reaction can compete with the corresponding unimolecular reaction below 240 K when the SO2 concentration is 9 × 1010 molecules per cubic centimeter. We also find that experimental results may not be sufficiently accurate for the unimolecular reaction of (CH3)2COO above 310 K. Not only does the present investigation provide insights into the decay of (CH3)2COO in the atmosphere, but it also provides an illustration of how to use theoretical methods to predict quantitative rate constants of medium-sized Criegee intermediates.
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Affiliation(s)
- Bo Long
- College of Materials Science and Engineering, Guizhou Minzu University, 550025 Guiyang, China;
- Department of Chemistry, Chemical Theory Center, University of Minnesota, Minneapolis, MN 55455-0431
- Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455-0431
| | - Junwei Lucas Bao
- Department of Chemistry, Chemical Theory Center, University of Minnesota, Minneapolis, MN 55455-0431
- Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455-0431
| | - Donald G Truhlar
- Department of Chemistry, Chemical Theory Center, University of Minnesota, Minneapolis, MN 55455-0431;
- Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455-0431
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28
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Sylvetsky N, Martin JML. Probing the basis set limit for thermochemical contributions of inner-shell correlation: balance of core-core and core-valence contributions. Mol Phys 2018. [DOI: 10.1080/00268976.2018.1478140] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Affiliation(s)
- Nitai Sylvetsky
- Department of Organic Chemistry, Weizmann Institute of Science, Reḥovot, Israel
| | - Jan M. L. Martin
- Department of Organic Chemistry, Weizmann Institute of Science, Reḥovot, Israel
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29
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Chan B, Simmie JM. Barriometry – an enhanced database of accurate barrier heights for gas-phase reactions. Phys Chem Chem Phys 2018; 20:10732-10740. [DOI: 10.1039/c7cp08045j] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The kinetics of many reactions are critically dependent upon the barrier heights for which accurate determination can be difficult. More than 100 accurate barriers are obtained with the high-level W3X-L composite procedure.
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Affiliation(s)
- Bun Chan
- Graduate School of Engineering
- Nagasaki University
- Nagasaki 852-8521
- Japan
| | - John M. Simmie
- School of Chemistry
- National University of Ireland
- Galway
- Ireland
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30
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Chan B. Use of Low-Cost Quantum Chemistry Procedures for Geometry Optimization and Vibrational Frequency Calculations: Determination of Frequency Scale Factors and Application to Reactions of Large Systems. J Chem Theory Comput 2017; 13:6052-6060. [DOI: 10.1021/acs.jctc.7b00721] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Bun Chan
- Graduate School of Engineering, Nagasaki University, Bunkyo 1-14, Nagasaki 852-8521, Japan
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31
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Ganyecz Á, Kállay M, Csontos J. Moderate-Cost Ab Initio Thermochemistry with Chemical Accuracy. J Chem Theory Comput 2017; 13:4193-4204. [DOI: 10.1021/acs.jctc.7b00607] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ádám Ganyecz
- MTA-BME Lendület Quantum
Chemistry Research Group, Department of Physical Chemistry and Materials
Science, Budapest University of Technology and Economics, Budapest, P.O. Box 91, H-1521 Hungary
| | - Mihály Kállay
- MTA-BME Lendület Quantum
Chemistry Research Group, Department of Physical Chemistry and Materials
Science, Budapest University of Technology and Economics, Budapest, P.O. Box 91, H-1521 Hungary
| | - József Csontos
- MTA-BME Lendület Quantum
Chemistry Research Group, Department of Physical Chemistry and Materials
Science, Budapest University of Technology and Economics, Budapest, P.O. Box 91, H-1521 Hungary
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32
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Chan B, Kawashima Y, Hirao K. Correlation functional in screened-exchange density functional theory procedures. J Comput Chem 2017; 38:2307-2315. [DOI: 10.1002/jcc.24882] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 05/27/2017] [Accepted: 06/23/2017] [Indexed: 02/01/2023]
Affiliation(s)
- Bun Chan
- Graduate School of Engineering; Nagasaki University; Bunkyo 1-14, Nagasaki-shi Nagasaki 852-8521 Japan
| | - Yukio Kawashima
- RIKEN Advanced Institute for Computational Science; 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe Hyogo 650-0047 Japan
| | - Kimihiko Hirao
- RIKEN Advanced Institute for Computational Science; 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe Hyogo 650-0047 Japan
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33
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Chan B. How to computationally calculate thermochemical properties objectively, accurately, and as economically as possible. PURE APPL CHEM 2017. [DOI: 10.1515/pac-2016-1116] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
We have developed the WnX series of quantum chemistry composite protocols for the computation of highly-accurate thermochemical quantities with advanced efficiency and applicability. The W1X-type methods have a general accuracy of ~3–4 kJ mol−1 and they can currently be applied to systems with ~20–30 atoms. Higher-level methods include W2X, W3X and W3X-L, with the most accurate of these being W3X-L. It can be applied to molecules with ~10–20 atoms and is generally accurate to ~1.5 kJ mol−1. The WnX procedures have opened up new possibilities for computational chemists in pursue of accurate thermochemical values in a highly-productive manner.
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Abstract
We have devised the composite procedures WG and WGh to unify the W1X and the (computationally more economical) G4(MP2)-6X protocols. The WG procedure employs a combination of MP2, MP2-F12, CCSD-F12b, and CCSD(T) to approximate the all-electron scalar-relativistic CCSD(T)/CBS energy. In addition, it incorporates features such as the scaling of the energy components and an empirical "higher-level-correction" term. The WGh protocol represents a somewhat more economical variant of WG with partial removal of diffuse functions. Our benchmark shows that, in general, both WG and WGh have similar performance to that for W1X-2, with WGh (predictably) performing somewhat less well for electron affinities. In terms of computational efficiency, WG is approximately an order of magnitude less costly than W1X-2, while WGh gives not only a further slight savings in computer time but also a notably reduced disk requirement.
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Affiliation(s)
- Bun Chan
- Graduate School of Engineering, Nagasaki University , Bunkyo 1-14, Nagasaki 852-8521, Japan
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35
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Bao JL, Xing L, Truhlar DG. Dual-Level Method for Estimating Multistructural Partition Functions with Torsional Anharmonicity. J Chem Theory Comput 2017; 13:2511-2522. [DOI: 10.1021/acs.jctc.7b00232] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Junwei Lucas Bao
- Department of Chemistry, Chemical Theory
Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Lili Xing
- Department of Chemistry, Chemical Theory
Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Donald G. Truhlar
- Department of Chemistry, Chemical Theory
Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
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36
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Chan B, Karton A, Raghavachari K, Radom L. Restricted-Open-Shell G4(MP2)-Type Procedures. J Phys Chem A 2016; 120:9299-9304. [DOI: 10.1021/acs.jpca.6b09361] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Bun Chan
- Graduate
School of Engineering, Nagasaki University, Bunkyo 1-14, Nagasaki 852-8521, Japan
| | - Amir Karton
- School
of Chemistry and Biochemistry, The University of Western Australia, Perth, WA 6009, Australia
| | - Krishnan Raghavachari
- Department
of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Leo Radom
- School
of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
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37
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Barrierless association of CF2 and dissociation of C2F4 by variational transition-state theory and system-specific quantum Rice-Ramsperger-Kassel theory. Proc Natl Acad Sci U S A 2016; 113:13606-13611. [PMID: 27834727 DOI: 10.1073/pnas.1616208113] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bond dissociation is a fundamental chemical reaction, and the first principles modeling of the kinetics of dissociation reactions with a monotonically increasing potential energy along the dissociation coordinate presents a challenge not only for modern electronic structure methods but also for kinetics theory. In this work, we use multifaceted variable-reaction-coordinate variational transition-state theory (VRC-VTST) to compute the high-pressure limit dissociation rate constant of tetrafluoroethylene (C2F4), in which the potential energies are computed by direct dynamics with the M08-HX exchange correlation functional. To treat the pressure dependence of the unimolecular rate constants, we use the recently developed system-specific quantum Rice-Ramsperger-Kassel theory. The calculations are carried out by direct dynamics using an exchange correlation functional validated against calculations that go beyond coupled-cluster theory with single, double, and triple excitations. Our computed dissociation rate constants agree well with the recent experimental measurements.
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38
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Long B, Bao JL, Truhlar DG. Atmospheric Chemistry of Criegee Intermediates: Unimolecular Reactions and Reactions with Water. J Am Chem Soc 2016; 138:14409-14422. [PMID: 27682870 DOI: 10.1021/jacs.6b08655] [Citation(s) in RCA: 196] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Criegee intermediates are produced in the ozonolysis of unsaturated hydrocarbons in the troposphere, and understanding their fate is a prerequisite to modeling climate-controlling atmospheric aerosol formation. Although some experimental and theoretical rate data are available, they are incomplete and partially inconsistent, and they do not cover the tropospheric temperature range. Here, we report quantum chemical rate constants for the reactions of stabilized formaldehyde oxide (CH2OO) and acetaldehyde oxide (syn-CH3CHOO and anti-CH3CHOO) with H2O and for their unimolecular reactions. Our results are obtained by combining post-CCSD(T) electronic structure benchmarks, validated density functional theory potential energy surfaces, and multipath variational transition state theory with multidimensional tunneling, coupled-torsions anharmonicity, and high-frequency anharmonicity. We consider two different types of reaction mechanisms for the bimolecular reactions, namely, (i) addition-coupled hydrogen transfer and (ii) double hydrogen atom transfer (DHAT). First, we show that the MN15-L exchange-correlation functional has kJ/mol accuracy for the CH2OO + H2O and syn-CH3CHOO + H2O reactions. Then we show that, due to tunneling, the DHAT mechanism is especially important in the syn-CH3CHOO + H2O reaction. We show that the dominant pathways for reactions of Criegee intermediates depend on altitude. The results we obtain eliminate the discrepancy between experiment and theory under those conditions where experimental results are available, and we make predictions for the full range of temperatures and pressures encountered in the troposphere and stratosphere. The present results are an important cog in clarifying the atmospheric fate and oxidation processes of Criegee intermediates, and they also show how theoretical methods can provide reliable rate data for complex atmospheric processes.
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Affiliation(s)
- Bo Long
- College of Information Engineering, Guizhou Minzu University , Guiyang 550025, China.,Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States
| | - Junwei Lucas Bao
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States
| | - Donald G Truhlar
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States
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Yu HS, Li SL, Truhlar DG. Perspective: Kohn-Sham density functional theory descending a staircase. J Chem Phys 2016; 145:130901. [DOI: 10.1063/1.4963168] [Citation(s) in RCA: 204] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Haoyu S. Yu
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA
| | - Shaohong L. Li
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA
| | - Donald G. Truhlar
- Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, USA
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Chan B, Radom L. Frequency Scale Factors for Some Double-Hybrid Density Functional Theory Procedures: Accurate Thermochemical Components for High-Level Composite Protocols. J Chem Theory Comput 2016; 12:3774-80. [DOI: 10.1021/acs.jctc.6b00554] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Bun Chan
- School
of Chemistry and ARC Centre of Excellence for Free Radical Chemistry
and Biotechnology, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Leo Radom
- School
of Chemistry and ARC Centre of Excellence for Free Radical Chemistry
and Biotechnology, University of Sydney, Sydney, New South Wales 2006, Australia
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41
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Sylvetsky N, Peterson KA, Karton A, Martin JML. Toward a W4-F12 approach: Can explicitly correlated and orbital-based ab initio CCSD(T) limits be reconciled? J Chem Phys 2016; 144:214101. [DOI: 10.1063/1.4952410] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Nitai Sylvetsky
- Department of Organic Chemistry, Weizmann Institute of Science, 76100 Reḥovot, Israel
| | - Kirk A. Peterson
- Department of Chemistry, Washington State University, Pullman, Washington 99164-4630, USA
| | - Amir Karton
- School of Chemistry and Biochemistry, The University of Western Australia, Perth, WA 6009, Australia
| | - Jan M. L. Martin
- Department of Organic Chemistry, Weizmann Institute of Science, 76100 Reḥovot, Israel
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42
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Chan B, Song JW, Kawashima Y, Hirao K. Performance of the OP correlation functional in relation to its formulation: Influence of the exchange component and the effect of incorporating same-spin correlations. J Comput Chem 2016; 37:1306-12. [DOI: 10.1002/jcc.24327] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 12/26/2015] [Accepted: 01/25/2016] [Indexed: 01/27/2023]
Affiliation(s)
- Bun Chan
- School of Chemistry; University of Sydney; New South Wales 2006 Australia
- RIKEN Advanced Institute for Computational Science; 7-1-26 Minatojima-minami-Machi, Chuo-Ku Kobe Hyogo 650-0047 Japan
| | - Jong-Won Song
- RIKEN Advanced Institute for Computational Science; 7-1-26 Minatojima-minami-Machi, Chuo-Ku Kobe Hyogo 650-0047 Japan
| | - Yukio Kawashima
- RIKEN Advanced Institute for Computational Science; 7-1-26 Minatojima-minami-Machi, Chuo-Ku Kobe Hyogo 650-0047 Japan
| | - Kimihiko Hirao
- RIKEN Advanced Institute for Computational Science; 7-1-26 Minatojima-minami-Machi, Chuo-Ku Kobe Hyogo 650-0047 Japan
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43
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Karton A. A computational chemist's guide to accurate thermochemistry for organic molecules. WILEY INTERDISCIPLINARY REVIEWS-COMPUTATIONAL MOLECULAR SCIENCE 2016. [DOI: 10.1002/wcms.1249] [Citation(s) in RCA: 134] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Amir Karton
- School of Chemistry and Biochemistry; The University of Western Australia; Perth WA Australia
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Chan B, Kawashima Y, Katouda M, Nakajima T, Hirao K. From C60 to Infinity: Large-Scale Quantum Chemistry Calculations of the Heats of Formation of Higher Fullerenes. J Am Chem Soc 2016; 138:1420-9. [DOI: 10.1021/jacs.5b12518] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Bun Chan
- School
of Chemistry, University of Sydney, Sydney, New South Wales 2006, Australia
- RIKEN Advanced Institute for Computational Science, 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Yukio Kawashima
- RIKEN Advanced Institute for Computational Science, 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Michio Katouda
- RIKEN Advanced Institute for Computational Science, 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Takahito Nakajima
- RIKEN Advanced Institute for Computational Science, 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
| | - Kimihiko Hirao
- RIKEN Advanced Institute for Computational Science, 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
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45
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Chan B, Goerigk L, Radom L. On the inclusion of post-MP2 contributions to double-Hybrid density functionals. J Comput Chem 2015; 37:183-93. [DOI: 10.1002/jcc.23972] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 05/19/2015] [Accepted: 05/21/2015] [Indexed: 01/18/2023]
Affiliation(s)
- Bun Chan
- School of Chemistry; The University of Sydney and Centre of Excellence for Free Radical Chemistry and Biotechnology; Sydney New South Wales 2006 Australia
| | - Lars Goerigk
- School of Chemistry; The University of Melbourne; Parkville Victoria 3010 Australia
| | - Leo Radom
- School of Chemistry; The University of Sydney and Centre of Excellence for Free Radical Chemistry and Biotechnology; Sydney New South Wales 2006 Australia
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Chan B, Radom L. W2X and W3X-L: Cost-Effective Approximations to W2 and W4 with kJ mol–1 Accuracy. J Chem Theory Comput 2015; 11:2109-19. [DOI: 10.1021/acs.jctc.5b00135] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Bun Chan
- School of Chemistry and ARC Centre
of Excellence for Free Radical Chemistry and Biotechnology, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Leo Radom
- School of Chemistry and ARC Centre
of Excellence for Free Radical Chemistry and Biotechnology, University of Sydney, Sydney, New South Wales 2006, Australia
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47
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Simmie JM, Somers KP. Benchmarking Compound Methods (CBS-QB3, CBS-APNO, G3, G4, W1BD) against the Active Thermochemical Tables: A Litmus Test for Cost-Effective Molecular Formation Enthalpies. J Phys Chem A 2015; 119:7235-46. [PMID: 25580800 DOI: 10.1021/jp511403a] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The theoretical atomization energies of some 45 CxHyOz molecules present in the Active Thermochemical Tables compilation and of particular interest to the combustion chemistry community have been computed using five composite model chemistries as titled. The species contain between 1-8 "heavy" atoms, and a few are conformationally diverse with up to nine conformers. The enthalpies of formation at 0 and 298.15 K are then derived via the atomization method and compared against the recommended values. In general, there is very good agreement between our averaged computed values and those in the ATcT; those for 1,3-cyclopentadiene exceptionally differ considerably, and we show from isodesmic reactions that the true value for 1,3-cyclopentadiene is closer to 134 kJ mol(-1) than the reported 101 kJ mol(-1). If one is restricted to using a single method, statistical measures indicate that the best methods are in the rank order G3 ≈ G4 > W1BD > CBS-APNO > CBS-QB3. The CBS-x methods do on average predict ΔfH(⊖)(298.15 K) within ≈5 kJ mol(-1) but are prone to occasional lapses. There are statistical advantages to be gained from using a number of methods in tandem, and all possible combinations have been tested. We find that the average formation enthalpy coming from using CBS-APNO/G4, CBS-APNO/G3, and G3/G4 show lower mean signed and mean unsigned errors, and lower standard and root-mean-squared deviations, than any of these methods in isolation. Combining these methods also leads to the added benefit of providing an uncertainty rooted in the chemical species under investigation. In general, CBS-APNO and W1BD tend to underestimate the formation enthalpies of target species, whereas CBS-QB3, G3, and G4 have a tendency to overestimate the same. Thus, combining CBS-APNO with a G3/G4 combination leads to an improvement in all statistical measures of accuracy and precision, predicting the ATcT values to within 0.14 ± 4.21 kJ mol(-1), thus rivalling "chemical accuracy" (±4.184 kJ mol(-1)) without the excessive cost associated with higher-level methods such as W1BD.
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48
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Bakowies D. Simplified Wave Function Models in Thermochemical Protocols Based on Bond Separation Reactions. J Phys Chem A 2014; 118:11811-27. [DOI: 10.1021/jp510249v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dirk Bakowies
- Laboratory of Physical Chemistry, ETH Zürich, CH 8093 Zürich, Switzerland
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49
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Morris M, Chan B, Radom L. Effect of Protonation State and Interposed Connector Groups on Bond Dissociation Enthalpies of Alcohols and Related Systems. J Phys Chem A 2014; 118:2810-9. [DOI: 10.1021/jp501256f] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Michael Morris
- School of Chemistry and ARC
Centre of Excellence for Free Radical Chemistry and Biotechnology, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Bun Chan
- School of Chemistry and ARC
Centre of Excellence for Free Radical Chemistry and Biotechnology, University of Sydney, Sydney, New South Wales 2006, Australia
| | - Leo Radom
- School of Chemistry and ARC
Centre of Excellence for Free Radical Chemistry and Biotechnology, University of Sydney, Sydney, New South Wales 2006, Australia
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Abstract
Computational prediction of condensed phase acidity is a topic of much interest in the field today. We introduce the methods available for predicting gas phase acidity and pKas in aqueous and non-aqueous solvents including high-level electronic structure methods, empirical linear free energy relationships (LFERs), implicit solvent methods, explicit solvent statistical free energy methods, and hybrid implicit–explicit approaches. The focus of this paper is on implicit solvent methods, and we review recent developments including new electronic structure methods, cluster-continuum schemes for calculating ionic solvation free energies, as well as address issues relating to the choice of proton solvation free energy to use with implicit solvation models, and whether thermodynamic cycles are necessary for the computation of pKas. A comparison of the scope and accuracy of implicit solvent methods with ab initio molecular dynamics free energy methods is also presented. The present status of the theory and future directions are outlined.
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