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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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Espinosa-Garcia J, Rangel C. The CN(X 2Σ+) + C2H6 reaction: Dynamics study based on an analytical full-dimensional potential energy surface. J Chem Phys 2023; 159:124307. [PMID: 38127394 DOI: 10.1063/5.0172489] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 09/14/2023] [Indexed: 12/23/2023] Open
Abstract
The hydrogen abstraction reaction of the cyano radical with molecules of ethane presents some interesting points in the chemistry from ultra-cold to combustion environments especially with regard to HCN(v) product vibrational distribution. In order to understand its dynamics, a new analytical full-dimensional potential energy surface was developed, named PES-2023. It uses a combination of valence bond and mechanic molecular terms as the functional form, fitted to high-level ab initio calculations at the explicitly correlated CCSD(T)-F12/aug-cc-pVTZ level on a reduced and selected number of points describing the reactive process. The new surface showed a continuous and smooth behavior, describing reasonably the topology of the reaction: high exothermicity, low barrier, and presence of intermediate complexes in the entrance and exit channels. Using quasi-classical trajectory calculations (QCT) on the new PES-2023, a dynamics study was performed at room temperature with special emphasis on the HCN(v1,v2,v3) product stretching and bending vibrational excitations, and the results were compared with the experimental evidence, which presented discrepancies in the bending excitation. The available energy was mostly deposited as HCN(v) vibrational energy with the vibrational population inverted in the CH stretching mode and not inverted in the CN stretching and bending modes, thus simulating the experimental evidence. Other dynamics properties at room temperature were also analyzed; cold rotational energy distribution was found, associated with a linear and soft transition state, and backward scattering distribution was found, associated with a rebound mechanism.
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Affiliation(s)
- Joaquin Espinosa-Garcia
- Área de Química Física and Instituto de Computación Científica Avanzada, Universidad de Extremadura, 06071 Badajoz, Spain
| | - Cipriano Rangel
- Área de Química Física and Instituto de Computación Científica Avanzada, Universidad de Extremadura, 06071 Badajoz, Spain
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Espinosa‐Garcia J. Kinetics study of the OH + SiH
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hydrogen abstraction reaction: A theoretical analysis. INT J CHEM KINET 2022. [DOI: 10.1002/kin.21593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Joaquín Espinosa‐Garcia
- Departamento de Química Física and Instituto de Computación Científica Avanzada Universidad de Extremadura Badajoz Spain
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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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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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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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Li J, Zhao B, Xie D, Guo H. Advances and New Challenges to Bimolecular Reaction Dynamics Theory. J Phys Chem Lett 2020; 11:8844-8860. [PMID: 32970441 DOI: 10.1021/acs.jpclett.0c02501] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Dynamics of bimolecular reactions in the gas phase are of foundational importance in combustion, atmospheric chemistry, interstellar chemistry, and plasma chemistry. These collision-induced chemical transformations are a sensitive probe of the underlying potential energy surface(s). Despite tremendous progress in past decades, our understanding is still not complete. In this Perspective, we survey the recent advances in theoretical characterization of bimolecular reaction dynamics, stimulated by new experimental observations, and identify key new challenges.
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Affiliation(s)
- Jun Li
- School of Chemistry and Chemical Engineering & Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University, Chongqing 401331, China
| | - Bin Zhao
- Theoretische Chemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, D-33615 Bielefeld, Germany
| | - Daiqian Xie
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Hua Guo
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
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Afshar Ghahremani F, Zahedi-Tabrizi M, Faramarz Tayyari S. The nature of intramolecular hydrogen bond in Naphthazarin. Chem Phys 2020. [DOI: 10.1016/j.chemphys.2020.110907] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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10
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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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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: 13] [Impact Index Per Article: 3.3] [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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Espinosa-Garcia J, Rangel C, Corchado JC, Garcia-Chamorro M. Theoretical study of the O( 3P) + C 2H 6 reaction based on a new ab initio-based global potential energy surface. Phys Chem Chem Phys 2020; 22:22591-22601. [PMID: 33000848 DOI: 10.1039/d0cp04125d] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new analytical potential energy surface was developed for the first time for the nine-body O(3P) + C2H6 hydrogen abstraction reaction, named PES-2020, which was fitted to explicitly-correlated high-level electronic structure calculations. This surface simulates the topography of the reactive system, from reactants to products, OH(v,j) + C2H5. The adiabatic energy of reaction, ΔHr(0 K) = -2.33 kcal mol-1, reproduces the experimental evidence, and the barrier height, 10.70 kcal mol-1, agrees with the ab initio calculations used as input. In addition, an intermediate complex in the exit channel is observed, which is stabilized with respect to the products of the reaction. Based on PES-2020 a dynamics study was carried out, where quasi-classical trajectory calculations were performed for collision energies in the range of 7.0-60.0 kcal mol-1, which covers high collision energy regions. The reaction cross section increases with collision energy; the largest fraction of available energy is deposited as translational energy (44-66%), and the scattering distribution evolves from backward to forward with collision energy. These findings reproduce previous theoretical calculations using electronic structure calculations of lower levels. However, where these previous studies failed, viz. in rotational and vibrational OH(v,j) distributions, PES-2020 reproduces practically quantitatively the experimental evidence, i.e., cold vibration and rotation, the rotational distribution peaking at j = 1-3 depending on the collision energy. In sum, this behaviour is typical of gas-phase hydrogen abstraction reactions with direct mechanism and high reaction barrier.
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Affiliation(s)
- J Espinosa-Garcia
- Departamento de Química Física and Instituto de Computación Científica Avanzada, Universidad de Extremadura, 06071 Badajoz, Spain.
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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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14
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Rangel C, Garcia-Chamorro M, Corchado JC, Espinosa-Garcia J. Kinetics and dynamics study of the OH + C 2H 6 → H 2O + C 2H 5 reaction based on an analytical global potential energy surface. Phys Chem Chem Phys 2020; 22:14796-14810. [PMID: 32578642 DOI: 10.1039/d0cp02776f] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
To describe the gas-phase hydrogen abstraction reaction between the hydroxyl radical and the ethane molecule, an analytical full-dimensional potential energy surface was developed within the Born-Oppenheimer approximation. This reactive process is a ten-body system with 24 degrees of freedom, which represents a theoretical challenge. The new surface, named PES-2020, presents low barrier, 3.76 kcal mol-1, high exothermicity, -16.20 kcal mol-1, and intermediate complexes in the entrance and exit channels. To test the quality and accuracy of the analytical surface several stringent tests were performed and, in general, PES-2020 reasonably simulates the theoretical information used as input, it is a continuous and smooth potential, without spurious minima, it presents great versatility and a reasonable description of this ten-body reaction. Based on this surface, an exhaustive kinetics and dynamics study was performed with a double objective: to analyze the capacity of the new surface to simulate the experimental evidence, and to help understand the mechanism of reaction and the role of the ethyl group in the reaction. In the kinetics study, three approaches were used: variational transition-state theory with multidimensional tunnelling (VTST/MT), ring polymer molecular dynamics (RPMD) and quasi-classical trajectory (QCT) results, in the temperature range 200-2000 K. There is general agreement between the three approaches and they reasonably simulate the experimental behaviour, which gives confidence to the fitness of the new surface to describe the system. In the dynamics study, QCT calculations were performed at 298 K for a direct comparison with the only experimental result reported. We found that ethyl fragment presents a noticeable internal energy (∼20%) and so cannot be considered as a spectator. The water product vibrational energy is reasonably reproduced, though when a level-by-level distribution is analyzed the agreement is only qualitative.
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Affiliation(s)
- C Rangel
- Departamento de Química Física and Instituto de Computación Científica Avanzada, Universidad de Extremadura, 06071 Badajoz, Spain.
| | - M Garcia-Chamorro
- Departamento de Química Física and Instituto de Computación Científica Avanzada, Universidad de Extremadura, 06071 Badajoz, Spain.
| | - J C Corchado
- Departamento de Química Física and Instituto de Computación Científica Avanzada, Universidad de Extremadura, 06071 Badajoz, Spain.
| | - J Espinosa-Garcia
- Departamento de Química Física and Instituto de Computación Científica Avanzada, Universidad de Extremadura, 06071 Badajoz, Spain.
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15
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Bonnet L, Larrégaray P, Lara M, Launay JM. Theoretical Study of Barrierless Chemical Reactions Involving Nearly Elastic Rebound: The Case of S( 1D) + X 2, X = H, D. J Phys Chem A 2019; 123:6439-6454. [PMID: 31329443 DOI: 10.1021/acs.jpca.9b04938] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
For some values of the total angular momentum consistent with reaction, the title processes involve nonreactive trajectories proceeding through a single rebound mechanism during which the internal motion of the reagent diatom is nearly unperturbed. When such paths are in a significant amount, the classical reaction probability is found to be markedly lower than the quantum mechanical one. This finding was recently attributed to an unusual quantum effect called diffraction-mediated trapping, and a semiclassical correction was proposed in order to take into account this effect in the classical trajectory method. In the present work, we apply the resulting approach to the calculation of opacity functions as well as total and state-resolved integral cross sections (ICSs) and compare the values obtained with exact quantum ones, most of which are new. As the title reactions proceed through a deep insertion well, mean potential statistical calculations are also presented. Seven values of the collision energy, ranging from 30 to 1127 K, are considered. Two remarkable facts stand out: (i) The corrected classical treatment strongly improves the accuracy of the opacity function as compared to the usual classical treatment. When the entrance transition state is tight, however, those trajectories crossing it with a bending vibrational energy below the zero point energy must be discarded. (ii) The quantum opacity function, particularly its cutoff, is finely reproduced by the statistical approach. Consequently, the total ICS is also very well described by the two previous approximate methods. These, however, do not predict state-resolved ICSs with the same accuracy, proving thereby that (i) one or several genuine quantum effects involved in the dynamics are missed by the corrected classical treatment and (ii) the dynamics are not fully statistical.
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Affiliation(s)
- L Bonnet
- Université de Bordeaux, ISM , UMR 5255, F-33400 Talence , France.,CNRS , ISM , UMR 5255, F-33400 Talence , France
| | - P Larrégaray
- Université de Bordeaux, ISM , UMR 5255, F-33400 Talence , France.,CNRS , ISM , UMR 5255, F-33400 Talence , France
| | - M Lara
- Departamento de Química Física Aplicada, Facultad de Ciencias , Universidad Autónoma de Madrid , 28049 Madrid , Spain
| | - J-M Launay
- Institut de Physique de Rennes, UMR CNRS 6251 , Université de Rennes I , F-35042 Rennes , France
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16
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Espinosa-Garcia J, Corchado JC. The hydrogen abstraction reaction H + C2H6 → H2(v,j) + C2H5. Part II. Theoretical kinetics and dynamics study. Phys Chem Chem Phys 2019; 21:13356-13367. [DOI: 10.1039/c9cp00701f] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two important issues motivated the present study: the role of the tunnelling contribution at low temperatures and the role of the alkyl fragment in the dynamics.
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Affiliation(s)
- Joaquin Espinosa-Garcia
- Área de Química Física and Instituto de Computacion Cientifica Avanzada
- Universidad de Extremadura
- 06071 Badajoz
- Spain
| | - Jose C. Corchado
- Área de Química Física and Instituto de Computacion Cientifica Avanzada
- Universidad de Extremadura
- 06071 Badajoz
- Spain
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17
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Espinosa-Garcia J, Garcia-Chamorro M, Corchado JC. The hydrogen abstraction reaction H + C2H6 → H2(v,j) + C2H5. Part I. A full-dimensional analytical potential energy surface based on ab initio calculations. Phys Chem Chem Phys 2019; 21:13347-13355. [DOI: 10.1039/c9cp00699k] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using as input data high-level structure electronic calculations, a new full-dimensional analytical potential energy surface (PES), named PES-2018, was developed for the title reaction, which is a valence bond/molecular mechanics based surface that depends on a set of adjustable parameters.
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Affiliation(s)
- Joaquin Espinosa-Garcia
- Área de Química Física and Instituto de Computacion Cientifica Avanzada
- Universidad de Extremadura
- 06071 Badajoz
- Spain
| | - Moises Garcia-Chamorro
- Área de Química Física and Instituto de Computacion Cientifica Avanzada
- Universidad de Extremadura
- 06071 Badajoz
- Spain
| | - Jose C. Corchado
- Área de Química Física and Instituto de Computacion Cientifica Avanzada
- Universidad de Extremadura
- 06071 Badajoz
- Spain
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18
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Papp D, Gruber B, Czakó G. Detailed benchmark ab initio mapping of the potential energy surfaces of the X + C2H6 [X = F, Cl, Br, I] reactions. Phys Chem Chem Phys 2019; 21:396-408. [DOI: 10.1039/c8cp06445h] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We provide benchmark relative energies for the stationary points of three different channels of the halogen atom + ethane reactions.
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Affiliation(s)
- Dóra Papp
- Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science
- Institute of Chemistry
- University of Szeged
- Szeged H-6720
- Hungary
| | - Balázs Gruber
- Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science
- Institute of Chemistry
- University of Szeged
- Szeged H-6720
- Hungary
| | - Gábor Czakó
- Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science
- Institute of Chemistry
- University of Szeged
- Szeged H-6720
- Hungary
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19
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Espinosa-Garcia J, Garcia-Chamorro M. Role of an ethyl radical and the problem of HF(v) bimodal vibrational distribution in the F(2P) + C2H6 → HF(v) + C2H5 reaction. Phys Chem Chem Phys 2018; 20:26634-26642. [DOI: 10.1039/c8cp05242e] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A theoretical study of the dynamics of the F(2P) + C2H6 hydrogen abstraction reaction was presented using quasi-classical trajectories propagated on an ab initio fitted global potential energy surface, PES-2018.
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Affiliation(s)
- J. Espinosa-Garcia
- Departamento de Quimica Fisica
- Instituto de Computacion Cientifica Avanzada
- Universidad de Extremadura
- 06071 Badajoz
- Spain
| | - M. Garcia-Chamorro
- Departamento de Quimica Fisica
- Instituto de Computacion Cientifica Avanzada
- Universidad de Extremadura
- 06071 Badajoz
- Spain
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