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Horváth K, Tajti V, Papp D, Czakó G. Dynamics of the HCl + C 2H 5 Multichannel Reaction on a Full-Dimensional Ab Initio Potential Energy Surface. J Phys Chem A 2024; 128:4474-4482. [PMID: 38807530 PMCID: PMC11163425 DOI: 10.1021/acs.jpca.4c02042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 05/13/2024] [Accepted: 05/15/2024] [Indexed: 05/30/2024]
Abstract
We report a full-dimensional ab initio analytical potential energy surface (PES), which accurately describes the HCl + C2H5 multichannel reaction. The new PES is developed by iteratively adding selected configurations along HCl + C2H5 quasi-classical trajectories (QCTs), thereby improving our previous Cl(2P3/2) + C2H6 PES using the Robosurfer program package. QCT simulations for the H'Cl + C2H5 reaction reveal hydrogen-abstraction, chlorine-abstraction, and hydrogen-exchange channels leading to Cl + C2H5H', H' + C2H5Cl, and HCl + C2H4H', respectively. Hydrogen abstraction dominates in the collision energy (Ecoll) range of 1-80 kcal/mol and proceeds with indirect isotropic scattering at low Ecoll and forward-scattered direct stripping at high Ecoll. Chlorine abstraction opens around 40 kcal/mol collision energy and becomes competitive with hydrogen abstraction at Ecoll = 80 kcal/mol. A restricted opening of the cone of acceptance in the Cl-abstraction reaction is found to result in the preference for a backward-scattering direct-rebound mechanism at all energies studied. Initial attack-angle distributions show mainly side-on collision preference of C2H5 for both abstraction reactions, and in the case of the HCl reactant, H/Cl-side preference for the H/Cl abstraction. For hydrogen abstraction, the collision energy transfer into the product translational and internal energy is almost equally significant, whereas in the case of chlorine abstraction, most of the available energy goes into the internal degrees of freedom. Hydrogen exchange is a minor channel with nearly constant reactivity in the Ecoll range of 10-80 kcal/mol.
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Affiliation(s)
- Kitti Horváth
- MTA-SZTE Lendület
Computational Reaction Dynamics Research Group, Interdisciplinary
Excellence Centre and Department of Physical Chemistry and Materials
Science, Institute of Chemistry, University
of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Viktor Tajti
- MTA-SZTE Lendület
Computational Reaction Dynamics Research Group, Interdisciplinary
Excellence Centre and Department of Physical Chemistry and Materials
Science, Institute of Chemistry, University
of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Dóra Papp
- MTA-SZTE Lendület
Computational Reaction Dynamics Research Group, Interdisciplinary
Excellence Centre and Department of Physical Chemistry and Materials
Science, Institute of Chemistry, University
of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Gábor Czakó
- MTA-SZTE Lendület
Computational Reaction Dynamics Research Group, Interdisciplinary
Excellence Centre and Department of Physical Chemistry and Materials
Science, Institute of Chemistry, University
of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
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Yin C, Czakó G. Theoretical vibrational mode-specific dynamics studies for the HBr + C 2H 5 reaction. Phys Chem Chem Phys 2023; 25:3083-3091. [PMID: 36620947 DOI: 10.1039/d2cp05334a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A quasi-classical trajectory (QCT) study is performed for the HBr + C2H5 multi-channel reaction using a recently-developed high-level ab initio full-dimensional spin-orbit-corrected potential energy surface (PES) by exciting five different vibrational modes of reactants at five collision energies. The effect of the normal-mode excitations on the reactivity, the mechanism, and the post-reaction energy flow is followed. A significant decrease of the reactivity caused by the longer initial distances of the reactants for the vHBr = 1 reaction at low collision energy (Ecoll) is observed due to the intramolecular vibrational-energy redistribution and the classical nature of the QCT method. All of the three reaction pathways (H-abstraction, Br-abstraction, and H-exchange) are intensely promoted when the HBr-stretching mode is excited. No clear promotion is observed when excitation is imposed to C2H5 except that asymmetric CH-stretching helps the H-exchange process. The enhancement effect of the excitation in the HBr vibrational mode is found to be much more effective than increasing the translational energy, in contrast to the HBr + CH3 reaction. The forward scattering mechanism can be clearly promoted by the excitation of the HBr-stretching mode, or by the high collision energy, indicating the dominance of the direct stripping mechanism in these cases. At low collision energy with no excitation or excitation of any vibrational mode of C2H5, the forward scattering feature is less obvious. At Ecoll = 1 kcal mol-1, when HBr-stretching is excited, the product clearly gains more relative translational energy. However, it is interesting to see that when the excitation is in C2H5, the effect is the opposite, i.e., the product gains less relative translational energy compared to the ground-state reaction.
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Affiliation(s)
- Cangtao Yin
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
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3
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Szűcs T, Czakó G. Benchmark ab initio potential energy surface mapping of the F + CH 3NH 2 reaction. Phys Chem Chem Phys 2022; 24:20249-20257. [PMID: 35975600 DOI: 10.1039/d2cp03006c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This electronic structure study reveals four exothermic and two endothermic reaction pathways of the F + CH3NH2 system: the barrierless hydrogen abstraction from the methyl/amino group (HF + CH2NH2/CH3NH), amino/methyl substitution (NH2 + CH3F and CH3 + NH2F) and hydrogen substitution from the two functional groups (H + CH2FNH2/CH3NHF). The benchmark classical and adiabatic energies are obtained using a high-accuracy composite ab initio approach, where the gold-standard explicitly-correlated coupled cluster method (CCSD(T)-F12b) is applied with the correlation-consistent polarized valence quintuple-zeta F12 basis set (cc-pV5Z-F12) and further additive energy contributions. Considering indispensable post-(T) correlation, core correlation, scalar relativistic, spin-orbit and harmonic zero-point energy corrections, the obtained global minimum of the potential energy surface is the post-reaction CH2NH2⋯HF complex in the product channel. Although each substitution pathway has a high barrier, the energies of amino-substitution and methyl-hydrogen-substitution products are below the energy of the reactants, as well as the submerged-barrier hydrogen-abstraction pathways.
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Affiliation(s)
- Tímea Szűcs
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
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Espinosa-Garcia J, Rangel C, Corchado JC. Current Status of the X + C 2H 6 [X ≡ H, F( 2P), Cl( 2P), O( 3P), OH] Hydrogen Abstraction Reactions: A Theoretical Review. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27123773. [PMID: 35744901 PMCID: PMC9228020 DOI: 10.3390/molecules27123773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/08/2022] [Accepted: 06/08/2022] [Indexed: 12/03/2022]
Abstract
This paper is a detailed review of the chemistry of medium-size reactive systems using the following hydrogen abstraction reactions with ethane, X + C2H6 → HX + C2H5; X ≡ H, F(2P), Cl(2P), O(3P) and OH, and focusing attention mainly on the theoretical developments. These bimolecular reactions range from exothermic to endothermic systems and from barrierless to high classical barriers of activation. Thus, the topography of the reactive systems changes from reaction to reaction with the presence or not of stabilized intermediate complexes in the entrance and exit channels. The review begins with some reflections on the inherent problems in the theory/experiment comparison. When one compares kinetics or dynamics theoretical results with experimental measures, one is testing both the potential energy surface describing the nuclei motion and the kinetics or dynamics method used. Discrepancies in the comparison may be due to inaccuracies of the surface, limitations of the kinetics or dynamics methods, and experimental uncertainties that also cannot be ruled out. The paper continues with a detailed review of some bimolecular reactions with ethane, beginning with the reactions with hydrogen atoms. The reactions with halogens present a challenge owing to the presence of stabilized intermediate complexes in the entrance and exit channels and the influence of the spin-orbit states on reactivity. Reactions with O(3P) atoms lead to three surfaces, which is an additional difficulty in the theoretical study. Finally, the reactions with the hydroxyl radical correspond to a reactive system with ten atoms and twenty-four degrees of freedom. Throughout this review, different strategies in the development of analytical potential energy surfaces describing these bimolecular reactions have been critically analyzed, showing their advantages and limitations. These surfaces are fitted to a large number of ab initio calculations, and we found that a huge number of calculations leads to accurate surfaces, but this information does not guarantee that the kinetics and dynamics results match the experimental measurements.
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Tóth P, Szűcs T, Czakó G. Benchmark Ab Initio Characterization of the Abstraction and Substitution Pathways of the Cl + CH 3CN Reaction. J Phys Chem A 2022; 126:2802-2810. [PMID: 35482972 PMCID: PMC9109142 DOI: 10.1021/acs.jpca.2c01376] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
We investigate the
reaction pathways of the Cl + CH3CN system: hydrogen abstraction,
methyl substitution, hydrogen substitution,
and cyanide substitution, leading to HCl + CH2CN, ClCN/CNCl
+ CH3, ClCH2CN + H, and CH3Cl + CN,
respectively. Hydrogen abstraction is exothermic and has a low barrier,
whereas the other channels are endothermic with high barriers. The
latter two can proceed via a Walden inversion or front-side attack
mechanism, and the front-side attack barriers are always higher. The
C-side methyl substitution has a lower barrier and also a lower endothermicity
than the N-side reaction. The computations utilize an accurate composite
ab initio approach and the explicitly correlated CCSD(T)-F12b method.
The benchmark classical and vibrationally adiabatic energies of the
stationary points are determined with the most accurate CCSD(T)-F12b/aug-cc-pVQZ
energies adding further contributions of the post-(T) and core correlation,
scalar relativistic effects, spin–orbit coupling, and zero-point
energy corrections. These contributions are found to be non-negligible
to reach subchemical accuracy.
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Affiliation(s)
- Petra Tóth
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Tímea Szűcs
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
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6
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Gao D, Wang D. Time-dependent quantum dynamics study of the F + C 2H 6 → HF + C 2H 5 reaction. Phys Chem Chem Phys 2021; 23:26911-26918. [PMID: 34825679 DOI: 10.1039/d1cp04212b] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction probabilities, integral cross sections, energy efficiency and rate constants are investigated for the F + C2H6 reaction using the quantum reaction dynamics, wave packet method. The ground-state integral cross section calculated using a six-degree-of-freedom approach is in very good agreement with the quasi-classical trajectory results. We find that the H-CH2CH3 stretching motion has the largest enhancement to reactivity, followed by the H-CH2-CH3 bending motion. However, the stretching motion between CH2 and CH3 slightly hinders the reactivity. The energy-form efficacy based on an equal amount of total energy shows that translational energy is more effective in enhancing the reactivity than vibrational energy of the H-CH2CH3 stretching motion at a relatively lower translational energy, while the reverse is true at a relatively high translational energy. An energy-shifting method is employed to calculate the full-dimensional rate constants. The quantum rate constants agree well with one of the two main experimental measurements, and the activation energy has an excellent agreement with the one calculated using canonical variational transition-state theory.
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Affiliation(s)
- Delu Gao
- College of Physics and Electronics, Shandong Normal University, Jinan 250014, Shandong, China.
| | - Dunyou Wang
- College of Physics and Electronics, Shandong Normal University, Jinan 250014, Shandong, China.
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7
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Papp D, Czakó G. Vibrational mode-specific dynamics of the F( 2P 3/2) + C 2H 6 → HF + C 2H 5 reaction. J Chem Phys 2021; 155:154302. [PMID: 34686045 DOI: 10.1063/5.0069658] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate the competing effect of vibrational and translational excitation and the validity of the Polanyi rules in the early- and negative-barrier F(2P3/2) + C2H6 → HF + C2H5 reaction by performing quasi-classical dynamics simulations on a recently developed full-dimensional multi-reference analytical potential energy surface. The effect of five normal-mode excitations of ethane on the reactivity, the mechanism, and the post-reaction energy flow is followed through a wide range of collision energies. Promoting effects of vibrational excitations and interaction time, related to the slightly submerged barrier, are found to be suppressed by the early-barrier-induced translational enhancement, in contrast to the slightly late-barrier Cl + C2H6 reaction. The excess vibrational energy mostly converts into ethyl internal excitation while collision energy is transformed into product separation. The substantial reaction energy excites the HF vibration, which tends to show mode-specificity and translational energy dependence as well. With increasing collision energy, direct stripping becomes dominant over the direct rebound and indirect mechanisms, being basically independent of reactant excitation.
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Affiliation(s)
- Dóra Papp
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
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8
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Papp D, Li J, Guo H, Czakó G. Vibrational mode-specificity in the dynamics of the Cl + C 2H 6 → HCl + C 2H 5 reaction. J Chem Phys 2021; 155:114303. [PMID: 34551541 DOI: 10.1063/5.0062677] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
We report a detailed dynamics study on the mode-specificity of the Cl + C2H6 → HCl + C2H5 H-abstraction reaction. We perform quasi-classical trajectory simulations using a recently developed high-level ab initio full-dimensional potential energy surface by exciting five different vibrational modes of ethane at four collision energies. We find that all the studied vibrational excitations, except that of the CC-stretching mode, clearly promote the title reaction, and the vibrational enhancements are consistent with the predictions of the Sudden Vector Projection (SVP) model, with the largest effect caused by the CH-stretching excitations. Intramolecular vibrational redistribution is also monitored for the differently excited ethane molecule. Our results indicate that the mechanism of the reaction changes with increasing collision energy, with no mode-specificity at high energies. The initial translational energy mostly converts into product recoil, while a significant part of the excess vibrational energy remains in the ethyl radical. An interesting competition between translational and vibrational energies is observed for the HCl vibrational distribution: the effect of exciting the low-frequency ethane modes, having small SVP values, is suppressed by translational excitation, whereas a part of the excess vibrational energy pumped into the CH-stretching modes (larger SVP values) efficiently flows into the HCl vibration.
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Affiliation(s)
- Dóra Papp
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Jun Li
- School of Chemistry and Chemical Engineering and Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 401331, China
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
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Czakó G, Győri T, Papp D, Tajti V, Tasi DA. First-Principles Reaction Dynamics beyond Six-Atom Systems. J Phys Chem A 2021; 125:2385-2393. [PMID: 33631071 PMCID: PMC8028310 DOI: 10.1021/acs.jpca.0c11531] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 02/05/2021] [Indexed: 11/29/2022]
Abstract
Moving beyond the six-atomic benchmark systems, we discuss the new age and future of first-principles reaction dynamics, which investigates complex, multichannel chemical reactions. We describe the methodology starting from the benchmark ab initio characterization of the stationary points, followed by full-dimensional potential energy surface (PES) developments and reaction dynamics computations. We highlight our composite ab initio approach providing benchmark stationary-point properties with subchemical accuracy, the Robosurfer program system enabling automatic PES development, and applications for the Cl + C2H6, F + C2H6, and OH- + CH3I post-six-atom reactions focusing on ab initio issues and their solutions as well as showing the excellent agreement between theory and experiment.
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Affiliation(s)
- Gábor Czakó
- MTA-SZTE Lendület
Computational Reaction Dynamics Research Group, Interdisciplinary
Excellence Centre and Department of Physical Chemistry and Materials
Science, Institute of Chemistry, University
of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Tibor Győri
- MTA-SZTE Lendület
Computational Reaction Dynamics Research Group, Interdisciplinary
Excellence Centre and Department of Physical Chemistry and Materials
Science, Institute of Chemistry, University
of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Dóra Papp
- MTA-SZTE Lendület
Computational Reaction Dynamics Research Group, Interdisciplinary
Excellence Centre and Department of Physical Chemistry and Materials
Science, Institute of Chemistry, University
of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Viktor Tajti
- MTA-SZTE Lendület
Computational Reaction Dynamics Research Group, Interdisciplinary
Excellence Centre and Department of Physical Chemistry and Materials
Science, Institute of Chemistry, University
of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Domonkos A. Tasi
- MTA-SZTE Lendület
Computational Reaction Dynamics Research Group, Interdisciplinary
Excellence Centre and Department of Physical Chemistry and Materials
Science, Institute of Chemistry, University
of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
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Szűcs T, Czakó G. Benchmark ab initio stationary-point characterization of the complex potential energy surface of the multi-channel Cl + CH 3NH 2 reaction. Phys Chem Chem Phys 2021; 23:10347-10356. [PMID: 33881412 DOI: 10.1039/d0cp06392d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We characterize the exothermic low/submerged-barrier hydrogen-abstraction (HCl + CH2NH2/CH3NH) as well as, for the first time, the endothermic high-barrier amino-substitution (CH3Cl + NH2), methyl-substitution (NH2Cl + CH3), and hydrogen-substitution (CH2ClNH2/CH3NHCl + H) pathways of the Cl + CH3NH2 reaction using an accurate composite ab initio approach. The computations reveal a CH3NH2Cl complex in the entrance channel, nine transition states corresponding to different abstractions, Walden-inversion substitution, and configuration-retaining front-side attack substitution pathways, as well as nine post-reaction complexes. The global minima of the electronic and vibrationally adiabatic potential energy surfaces correspond to the pre-reaction CH3NH2Cl and post-reaction CH2NH2HCl complexes, respectively. The benchmark composite energies of the stationary points are obtained by considering basis-set effects up to the correlation-consistent polarized valence quadruple-zeta basis augmented with diffuse functions (aug-cc-pVQZ) using the explicitly-correlated coupled-cluster singles, doubles, and perturbative triples CCSD(T)-F12b method, post-(T) correlation up to CCSDT(Q) including full triples and perturbative quadruples, core correlation, and scalar relativistic and spin-orbit effects, as well as harmonic zero-point energy corrections.
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Affiliation(s)
- Tímea Szűcs
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
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11
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Papp D, Czakó G. Full-dimensional MRCI-F12 potential energy surface and dynamics of the F(2P3/2) + C2H6 → HF + C2H5 reaction. J Chem Phys 2020; 153:064305. [DOI: 10.1063/5.0018894] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Dóra Papp
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H 6720, Hungary
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H 6720, Hungary
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12
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Espinosa-Garcia J, Garcia-Chamorro M, Corchado JC, Bhowmick S, Suleimanov YV. VTST and RPMD kinetics study of the nine-body X + C 2H 6 (X ≡ H, Cl, F) reactions based on analytical potential energy surfaces. Phys Chem Chem Phys 2020; 22:13790-13801. [PMID: 32538410 DOI: 10.1039/d0cp02238a] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Thermal rate constants of nine-atom hydrogen abstraction reactions, X + C2H6 → HX + C2H5 (X ≡ H, Cl, F) with qualitatively different reaction paths, have been investigated using two kinetics approaches - variational transition state theory with multidimensional tunnelling (VTST/MT) and ring polymer molecular dynamics (RPMD) - and full dimensional analytical potential energy surfaces. For the H + C2H6 reaction, which proceeds through a noticeable barrier height of 11.62 kcal mol-1, kinetics approaches showed excellent agreement between them (with differences less than 30%) and with the experiment (with differences less than 60%) in the wide temperature range of 200-2000 K. For X = Cl and F, however, the situation is very different. The barrier height is either low or very low, 2.44 and 0.23 kcal mol-1, respectively, and the presence of van der Waals complexes in the entrance channel leads to a very flat topography and, consequently, imposes theoretical challenges. For the Cl(2P) reaction, VTST/MT underestimates the experimental rate constants (with differences less than 86%), and RPMD demonstrates better agreement (with differences less than 47%), although the temperature dependence is opposite to the experiment at low temperatures. Finally, for the F(2P) reaction, available experimental information shows discrepancies, both in the absolute values of the rate constants and also in the temperature dependence. Unfortunately, kinetics theories did not resolve this discrepancy. Different possible causes of these theory/experiment discrepancies were analyzed.
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Affiliation(s)
- Joaquin Espinosa-Garcia
- Departamento de Quimica Fisica and Instituto de Computacion Cientifica Avanzada, Universidad de Extremadura, 06071 Badajoz, Spain.
| | - Moises Garcia-Chamorro
- Departamento de Quimica Fisica and Instituto de Computacion Cientifica Avanzada, Universidad de Extremadura, 06071 Badajoz, Spain.
| | - Jose C Corchado
- Departamento de Quimica Fisica and Instituto de Computacion Cientifica Avanzada, Universidad de Extremadura, 06071 Badajoz, Spain.
| | - Somnath Bhowmick
- Computation-based Science and Technology Research Center, The Cyprus Institute, 20 Konstantinou Kavafi Street, Nicosia 2121, Cyprus.
| | - Yury V Suleimanov
- Computation-based Science and Technology Research Center, The Cyprus Institute, 20 Konstantinou Kavafi Street, Nicosia 2121, Cyprus.
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13
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Papp D, Tajti V, Győri T, Czakó G. Theory Finally Agrees with Experiment for the Dynamics of the Cl + C 2H 6 Reaction. J Phys Chem Lett 2020; 11:4762-4767. [PMID: 32441943 PMCID: PMC7309313 DOI: 10.1021/acs.jpclett.0c01263] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 05/22/2020] [Indexed: 05/07/2023]
Abstract
Since the pioneering reaction dynamics studies of H + H2 in the 1970s, theory increased the system size by one atom in every decade arriving to six-atom reactions in the early 2010s. Here, we take a significant step forward by reporting accurate dynamics simulations for the nine-atom Cl + ethane (C2H6) reaction using a new high-quality spin-orbit-ground-state ab initio potential energy surface. Quasi-classical trajectory simulations on this surface cool the rotational distribution of the HCl product molecules, thereby providing unprecedented agreement with experiment after several previous failed attempts of theory. Unlike Cl + CH4, the Cl + C2H6 reaction is exothermic with an adiabatically submerged transition state, allowing testing of the validity of the Polanyi rules for a negative-barrier reaction.
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Affiliation(s)
- Dóra Papp
- MTA-SZTE Lendület Computational
Reaction Dynamics Research Group, Interdisciplinary Excellence Centre
and Department of Physical Chemistry and Materials Science, Institute
of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Viktor Tajti
- MTA-SZTE Lendület Computational
Reaction Dynamics Research Group, Interdisciplinary Excellence Centre
and Department of Physical Chemistry and Materials Science, Institute
of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Tibor Győri
- MTA-SZTE Lendület Computational
Reaction Dynamics Research Group, Interdisciplinary Excellence Centre
and Department of Physical Chemistry and Materials Science, Institute
of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
| | - Gábor Czakó
- MTA-SZTE Lendület Computational
Reaction Dynamics Research Group, Interdisciplinary Excellence Centre
and Department of Physical Chemistry and Materials Science, Institute
of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary
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14
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Czakó G, Győri T, Olasz B, Papp D, Szabó I, Tajti V, Tasi DA. Benchmark ab initio and dynamical characterization of the stationary points of reactive atom + alkane and SN2 potential energy surfaces. Phys Chem Chem Phys 2020; 22:4298-4312. [DOI: 10.1039/c9cp04944d] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We review composite ab initio and dynamical methods and their applications to characterize stationary points of atom/ion + molecule reactions.
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Affiliation(s)
- Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group
- Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science
- Institute of Chemistry
- University of Szeged
- Szeged H-6720
| | - Tibor Győri
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group
- Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science
- Institute of Chemistry
- University of Szeged
- Szeged H-6720
| | - Balázs Olasz
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group
- Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science
- Institute of Chemistry
- University of Szeged
- Szeged H-6720
| | - Dóra Papp
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group
- Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science
- Institute of Chemistry
- University of Szeged
- Szeged H-6720
| | - István Szabó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group
- Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science
- Institute of Chemistry
- University of Szeged
- Szeged H-6720
| | - Viktor Tajti
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group
- Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science
- Institute of Chemistry
- University of Szeged
- Szeged H-6720
| | - Domonkos A. Tasi
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group
- Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science
- Institute of Chemistry
- University of Szeged
- Szeged H-6720
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15
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Gruber B, Czakó G. Benchmark ab initio characterization of the abstraction and substitution pathways of the OH + CH4/C2H6 reactions. Phys Chem Chem Phys 2020; 22:14560-14569. [DOI: 10.1039/d0cp02560g] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report benchmark ab initio stationary-point properties for the hydrogen-abstraction, hydrogen-substitution, and methyl-substitution pathways of the OH + CH4/C2H6 reactions.
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Affiliation(s)
- Balázs Gruber
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group
- Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science
- Institute of Chemistry
- University of Szeged
- Szeged H-6720
| | - Gábor Czakó
- MTA-SZTE Lendület Computational Reaction Dynamics Research Group
- Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science
- Institute of Chemistry
- University of Szeged
- Szeged H-6720
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16
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Jasper AW, Sivaramakrishnan R, Klippenstein SJ. Nonthermal rate constants for CH 4 * + X → CH 3 + HX, X = H, O, OH, and O 2. J Chem Phys 2019; 150:114112. [PMID: 30902010 DOI: 10.1063/1.5090394] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Quasiclassical trajectories are used to compute nonthermal rate constants, k*, for abstraction reactions involving highly-excited methane CH4 * and the radicals H, O, OH, and O2. Several temperatures and internal energies of methane, Evib, are considered, and significant nonthermal rate enhancements for large Evib are found. Specifically, when CH4 * is internally excited close to its dissociation threshold (Evib ≈ D0 = 104 kcal/mol), its reactivity with H, O, and OH is shown to be collision-rate-limited and to approach that of comparably-sized radicals, such as CH3, with k* > 10-10 cm3 molecule-1 s-1. Rate constants this large are more typically associated with barrierless reactions, and at 1000 K, this represents a nonthermal rate enhancement, k*/k, of more than two orders of magnitude relative to thermal rate constants k. We show that large nonthermal rate constants persist even after significant internal cooling, with k*/k > 10 down to Evib ≈ D0/4. The competition between collisional cooling and nonthermal reactivity is studied using a simple model, and nonthermal reactions are shown to account for up to 35%-50% of the fate of the products of H + CH3 = CH4 * under conditions of practical relevance to combustion. Finally, the accuracy of an effective temperature model for estimating k* from k is quantified.
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Affiliation(s)
- Ahren W Jasper
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Raghu Sivaramakrishnan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Stephen J Klippenstein
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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